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Summer 2005 NCAC Newsletter 1

NewsletterNational Council of Acoustical Consultants Summer 2005

“Enhancing the stature and effectiveness of the acoustical consulting profession for the mutual benefi t of the publicand the member fi rms”

Mission:

Visit us at www.ncac.com

Highlights

President’s Summer Message

Established in 1962

Reverberation: Theory and MeasurementPage 4

Saint Martin’s Episcopal Church, Houston, TX0

Acoustical Consulting Advice Series – Part 2Page 12

Member’s In The NewsPage 15

ASTM E336 Standard is RevisedPage 23

By Edward Logsdon, P.E.

The NCAC Board of Directors meeting and the General Mem-bership meeting were held in

Vancouver, prior to the 149th Meeting of the Acoustical Society of America (ASA). At the Board of Directors (BOD) meeting, there was a long list of agen-da items to cover involving member-ship, long range planning, fi nances, and NCAC awards. Financially, NCAC is doing well, with more than $100,000 in our savings account. This is a considerable sum, but possible future expenditures – related to the management of NCAC and improved educational programs – are currently be-ing discussed that will make good use of some of the funds. Dave Conant, NCAC Vice President of Finance, provided a good summary of the fi nances at the meeting and an even better overview of the “Financial Health at NCAC” in the last Newsletter. His involvement in monitoring the fi nances will help ensure that whatever we decide will maximize the benefi t from any fi nancial expendi-ture. Other topics discussed at the BOD meeting included the update of the NCAC Directory. The Directory will be made available on the public area of the NCAC website as a downloadable Adobe .pdf fi le. The search engine for a consultant will still be available to those not needing a directory. To keep the fi le size reasonable, the color graphics on the front cover of the Directory will be elim-inated. Currently, the Directory is being updated to refl ect the Branch offi ce list-ings. Once completed, it will be posted to the website and an announcement will

be sent to the membership. If a member fi rm identifi es an error, they can notify NCAC headquarters and the fi le can be easily revised and re-uploaded to the website. This will also allow the mem-bership list to be revised as new mem-bers are accepted into NCAC – which brings me to the next topic. NCAC currently has 140 member fi rms. In Vancouver, we received applica-tions for both new fi rm and new individ-ual members. This is a good indication that others are seeing the value of the organization and wish to join. Certainly, the NCAC member forum is “worth the cost of admission.” We welcome more participation by qualifi ed fi rms and in-dividuals, as the organization is only as strong as our membership. NCAC headquarters currently has approximately 400 color brochures avail-able. These are available at cost to our members, to assist with educating poten-tial clients about the acoustical consult-ing profession. Basically, the informa-

Continues on page 2

2 Summer 2005 NCAC Newsletter

The NCAC Newsletter is published quarterly by the

National Council ofAcoustical Consultants as a service

to its membership and all interested parties.

2004-2006 NCACOffi cers/Directors

Edward L. LogsdonPresident

David E. MarshPresident-Elect

Kerrie G. StandleeVice President/Membership

David A. ConantVice President/Finance

Russ BergerVice President/Marketing

and Communications

Directors-at-LargeBennett M. Brooks

Neil Thompson ShadeBill Dohn

James E. PhillipsIndividual Representative

K. Anthony HooverImmediate Past President

Peter Allen Executive Director

Neil Thompson ShadeEditor

William CavanaughAssociate Editor

Tony RosaNewsletter Graphics & Layout

Headquarters66 Morris Ave., Suite 1A

Springfi eld, NJ 07081(973) 564-5859 • FAX (973) 564-7480

www.ncac.com E-mail [email protected]

tion contained in the brochure addresses who we are, what we do, and when the client should consider the services of an acoustical consultant. As the printed cop-ies of the brochure are exhausted, we can decide if more are needed or if it would be better to provide an electronic version of the brochure. Finally, the BOD reviewed the schedule for the up and coming ASA conferences. It was decided unanimously

to hold our next General Membership meeting in conjunction with the ASA Hawaii conference in the Fall 2006. Start now with your plans to attend! There will be teleconference meetings with the Board of Directors between now and then to address the business of the orga-nization. Also, NCAC may plan smaller events at the ASA meetings to be held in Minneapolis, MN and Providence, RI. Watch your emails for announcements.

By Neil Thompson Shade

Summer brings about a plethora of new movies, but cinematic “art” is not what I fi nd distressing. Is it

just in my community (Baltimore), but are movies getting substantially louder? Whether I go to the local multiplex, the 600-seat single screen Senator Theater, or the downtown art house, the sound levels seem higher than I ever remember. Some of this is due to the timbral balance and soundtrack compression, which gives the impression of greater loudness, but the overall playback lev-els are simply too high for my listening comfort. The levels seem highest dur-ing the upcoming previews and for the “blockbuster” action fi lms. At the end of some movies, I have actually experi-enced the sensation of temporary thresh-old shift. Letters of complaint to movie theater management have gone unan-swered. I would appreciate hearing from other NCAC members regarding their movie-going experience. This Newsletter starts a two-part reprint of Manfred Schroeder’s Distin-guished Lectures presented at the 1994 Sabine Centennial in celebration of a

special session to be held on diffusion at the Fall ASA meeting. Newsletter tech-nical topics cover acoustical software, highlights of ASTM E-336 revisions, and the acoustic design of a large cathedral. The issue continues with viewpoints on noise levels and hearing conservation with a guest editorial by Les Bloomberg

of Noise Pollution Clearinghouse and an article by Laymon Miller. NCAC mem-bers are highlighted to include honor-ary memberships for M. David Egan, Minoru Nagata, and George Paul Wilson and profi les of Newman Student Fund member Carl Rosenberg and NCAC Board Member Bill Dohn. Previous fea-tures from the last Newsletter continue with more of Eric Ungar’s humorous A to Z acoustical prose and acoustical con-sulting advice from former Bolt Beranek and Newman members. As always, your comments, news items, and concerns should be addressed to the editor at [email protected] [NTS]

Continued from page 1

From the Editor

President’s Message


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Continues on page 5

Schedule . . . looking ahead

Meeting Location Dates

Fall 2005 Minneapolis, MN* ASA, October 17-21, 2005

Spring 2006 Providence, Rhode Island* ASA, June 2006

Fall 2006 Hawaii* ASA, November 28-December 2, 2006

* NCAC Activities TBA

A Distinguished Lecture delivered at the Wallace Clement Sabine Centen-nial Symposium in June 1994 at the Massachusetts Institute of Technology.

Manfred Schroeder

Drittes Physikalisches InstitutUniversity of Gottingen, Germanyand AT& T Bell Laboratories (ret.)

Editor’s Note: The NCAC Newsletter is reprinting Manfred Schroeder’s two part Distinguished Lecture presented at the 1994 Sabine Centennial sponsored by the Acoustical Society of America. The Summer 2005 Newsletter contains Part 1 and the Fall 2005 Newsletter will contain Part 2. The reprinting, with per-mission from the author and ASA, is to preview a special session on sound dif-fusing surfaces to occur at the Fall 2005 ASA meeting, in part to commemorate Manfred Schroeder and the publishing of his ASA paper of 30 years ago on num-ber theory sound diffusing surfaces. The author’s biography appears at the end of this paper. [NTS]

PART I, REVERBERATION AND RAY THEORIES

REVERBERATION THEORY Reverberation time was both defi ned and measured by Wallace Clement Sa-bine [1] whom we celebrate this week. Reverberation time, the time interval for sound energy in an enclosure to decay by a factor of 106 or 60 dB is clearly the most important-and most widely quoted-room acoustical parameter. Build a lec-ture hall with a reverberation time of 3 seconds and speech in the reverberant fi eld will be unintelligible. Listen to a broadcast of an out-of-doors symphonic concert (without artifi cially added rever-beration) and it will sound awful. A reverberation time of 2 seconds is considered ideal for the classical rep-ertoire (Mozart et al.), while romantic symphonies require a bit more reverbera-tion. Organ music is typically written to be performed in churches and large cathedrals with reverberation times of 4 seconds or more. Fine! But listen to a

fast Baroque piece in St. Paul’s Cathe-dral: the resulting “mush” defi es descrip-tion (as music) unless one can move in very close to the players so that the direct (unreverberated) sound dominates. For whatever reason, people prefer rever-beration times to rise toward the low fre-quencies because it is said to give—and it does give—a more pleasing, “warmer” sound. Reverberation time is of course a rather summary description of the re-verberation process, which consists of direct sound, early (traceable) refl ections and reverberation proper, a statistical mishmash of late arriving sound energy. Research during the last few decades has, rightly, emphasized the importance of the early part of the impulse response. Psychophysical comparisons have shown that the fi rst 150 or so milliseconds really determine the subjective impression of reverberancy. In fact, for running music, any reverberation 5 or 10 dB below the ongoing music is masked by it and there-fore inaudible. Hence, the initial decay time, defi ned over the fi rst 10 dB of the decay, has come to the fore and is now widely adopted.

RAY THEORIES In a few simple geometries (“shoe-boxes”, hemispheres and the like), the

wave equation can be solved explicitly and the reverberation time calculated from the complex eigenvalues. This ap-proach is of little consequence to the acoustics of large rooms. Rather, the the-oretician is reduced to work with sound rays and he is further forced to make cer-tain statistical assumptions- often wildly unrealistic-as we shall see. Consider a sound source emitting K rays into as many different direc-tions. Each time a ray hits an absorber,

its energy is reduced by a factor ( )α−1, where α is the absorption coeffi cient, considered, for the moment, uniform and independent of the angle of incidence. If the initial total energy E0. is subdivided equally between the K rays, then the en-ergy remaining after a time interval t (ne-glecting sound absorption in the air by Knudson-Kneser relaxation) is given by

where n(t) is the number of collisions of the rays with the absorbing surfaces. Of course, different rays can be expected to have different collision numbers, but Eq. (1) ignores that fact. Furthermore, the

Reverberation: Theory and Measurement

(1)tnK

kKEtE

10 11


exponent n(t) is replaced by its expected value:

where l is the mean free path of the sound rays between successive encoun-ters with an absorber. What is this mean free path? Sabine originally conjectured that it was pro-

portional to the cube root 3/1V of the enclosure’s volume V, the cube root giv-ing him a length, which has the right di-mension. But on second thought, l must also depend, inversely, on the absorber surface area S. Thus, l ~ V/S is a better guess. Calculating l for a simple shape,

(2)

such as a sphere, one sees that the factor must be 4:

Here A is the cross-sectional area of the sphere. This formula was originally de-rived and shown to be valid for arbitrary shapes by Clausius in statistical me-chanics (where it is needed to calculate the pressure of a gas on the walls of a container from the molecular collisions). The astounding thing here is that l is independent of the enclosure’s shape for a given ratio V/S, a fact also shown by Kosten [2], reinventing a result from a branch of mathematics known as “inte-gral geometry”.

Inserting Eqs. (2) and (3) into (1) and calculating the time Ts it takes for the energy to decay to one millionth of its initial value gives

where we have made the further sim-plifi cation (valid for small α ) of ap-proximating the natural logarithm by α− . For different absorption coef-fi cients, Sabine replaced α by its aver-

age value α . This then is Sabine’s justly famous reverberation time formula. Without the approximation of the logarithm, i.e. if we recognize sound ab-sorption at surfaces as a discrete event

(3)

(4)


On Reverberation

Continues on page 6

cttn SV

AV 4

ScVTs

48.13

1ln

l


with fi nite-size steps, we obtain the for-mula by Fokker [3], Waetzmann and Schuster, and Eyring [4] in which α is properly replaced by the absorption ex-ponent . For 1=α , i.e. “empty space”, Eyring’s formula gives,

correctly, 0=ET (as opposed to Sabi-ne’s formula, which gives a wrong value

0>ST ). However, Eyring does not solve all of our problems. One remaining ques-tion is how to average absorption if the enclosure sports different values of the absorption exponent α . Millington [5] and Sette [5] replaced α by its average

value α , which is the correct procedure

if sound rays hit the different absorb-ers in temporal succession, as would be the case in a long corridor with com-pletely refl ective side walls and its two ends having different absorption expo-nents. But the Millington-Sette result is incorrect in the general case in which the energies of different sound rays are absorbed in parallel. The Millington-Sette formula goes out the window, so to speak, if one opens just one window in the room: The open window has 1=α and therefore ∞=a , so that averaging

of absorption exponents gives ∞=aand T = 0, a clearly absurd result. So what to do? Somehow it seems to make better sense (forgetting about long corridors) to average the absorption coef-fi cients in the Eyring formula. This yields

a widely used equation. The unanswered question is of course how can we pos-sibly justify (area-weighted) averaging inside the logarithm. The area, S, after all, sits outside the logarithm in Eq. (5). The solution of this riddle-a major tri-umph in reverberation theory-came from Andree [7], Kraak, and Kuttruff [8]: go back to Eq. (1) and consider the number of refl ections to be different for different rays and replace n(t) by nk(t). Assuming


Continues on page 7

(5)

Schroeder

SVTE 1ln

48.13

1lna


the nk to be multinomially distributed, as Kraak and Kuttruff did, accomplishes the long sought-after “miracle” of averag-ing inside the logarithm without further foul play. There is only one minor remaining problem with the multinomial distribu-tion: it supposes that the total number of refl ections is deterministically given:

In reality, as Monte Carlo ray simula-tions by Atal and Schroeder [9], and Kut-truff [10] have shown, this sum is also a random variable and fl uctuates consid-erably around its mean value. But how

Continued from page 6 does it fl uctuate? That-heavens forbid-depends on the geometry, the shape of the enclosure, and only the heavens seem to know how. Let us therefore play dice with the rays and assume that the total number of refl ections is distributed according to a Poisson distribution, the simplest law not requiring further unknown parame-ters [11]. The result? Irony of ironies: we are thrown all the way back to Sabine’s formula, which we already recognized as defi cient, a defi ciency that started us on the present trek. So there must be something wrong with the Poisson distribution, too, and it is easy to see what it is: the Poisson distribution gives non-vanishing prob-abilities for arbitrarily large numbers of refl ections-an impossibility for a fi nite

sound velocity. At this point in our de-liberations we come to the inescapable conclusion: we must “face the music” and calculate-either theoretically by tak-ing better account of the geometry of the enclosure or by computer ray simulation. Using the classical reverberation time formulas, which ignore geometry beyond volume and surface areas, is fraught with danger-expensive dangers. Fortunately, in many cases, it is not necessary to know the exact distribution of the number of refl ections n(t). Apart from the known mean value cSt/4V, the variance of the n(t)-distribution may suffi ce in most cases. As Atal [12] has pointed out, the logarithm of the energy as a function of time, expanded into a power series, is given by the so-called

Continues on page 8

(6)

On Reverberation

.41

tV

cStnK

kk


statistical cumulants ( )trκ of the n(t )-distribution:

where a is again the absorption expo-nent. Assuming the decay to be exponen-tial, Eq. (7) can be used to calculate the reverberation time:

where ( )1== trr κκ . The fi rst cumu-

lant 1κ equals the mean cS/4V of the n(t)-distribution for t=1; the second cu-

mulant 2κ equals its variance 2σ . Thus we get the following interesting expan-sion

where the three dots indicate higher-or-der terms proportional to a3 etc. Hence, to get a more accurate value of T, we have to include at least an estimate of the

refl ection-number variance 2σ , which does depend on the enclosure’s geometry beyond volume and surface area. Implicit in all of the foregoing is the assumption that sound fi elds are “dif-fuse” and that equal surface areas are hit with equal probability. Regrettably, this assumption is often violated, especially in enclosures, such as concert halls, in which the absorption is nonuniformly distributed, as Cremer [13] has pointed out early on. To cope with this misde-meanor, Kuttruff [10] and Joyce [14] have formulated integral equations for the variable ‘‘insonifi cation” of differ-ent surfaces. Schroeder and Hackman [15] solved such integral equations for a few simple two-dimensional enclosures, using an ingenious iterative method sug-gested by Gilbert [16]. In one such calcu-lation the reverberation time increased by 45% by just moving a single sound


(7)

(8)

(9)

absorbing “panel” to another (nearby) lo-cation. The reason for this substantial ef-fect was that in the second confi guration, the sound energy incident on the panel that was moved dropped by 30% while the sound incident on the nonabsorbing walls actually increased.

Manfred R. Schroeder studied mathematics and physics at the University of Goettin-

gen, where he obtained his doctorate in Physics in 1954. His thesis concerned the Wigner distribution of normal modes, characteristics of chaotic systems, in electromagnetic cavities and concert halls. Subsequent work on wave trans-mission in random media laid the foun-dation of a statistical wave theory char-acterized by a critical frequency, now called the Schroeder-frequency. In 1954, he joined Bell Laboratories, where his work included linear predic-tive coding for digital speech synthesis, monaural phase effects in hearing, and sound transmission in concert halls. After 5 years as Head of Acoustics Research, in 1963 he was appointed Director of the Acoustics, Speech and Mechanics Research Laboratory at Bell. In 1969, he was appointed Professor of Physics and Director of the Dritte Physikalisches Institut of the University of Goettingen, where he developed “quadratic-residue” diffusors (based on number theory) for optimally scattering radar and sound waves. Schroeder’s book “Number Theory in Science and Communication” won critical acclaim, as did his “Fractal, Chaos, Power Laws: Minutes from an Infi nite Paradise”. His computer graph-ics won First Prize at the 1969 Interna-tional Computer Art Competition. He is a founding member of the Institut de Recherche et Coordination Acoustique/Musique de Center Pompidou in Paris, a member of the Goettingen Academy of Science, the National Academy of Engi-neering (Washington, D.C.), and the Max Planck Society (Germany). He is a Fel-low of the New York Academy and the American Academy of Arts and Scienc-es. In 1972, he received the Gold Medal of the Audio Engineering Society, and in 1987 he was awarded the Lord Rayleigh Medal by the British Institute of Acous-tics. In 1991, he received the Gold Medal of the Acoustical Society of America “for theoretical and practical contribu-tions to human communication through innovative application of mathematics, to speech, hearing and concert hall acous-tics”.

On ReverberationAbout the author.

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Quiet Solution materials – labo-ratory tested and fi eld verifi ed

Editor’s Note: Information is provided to the Editor for review and editing prior to inclusion in the Newsletter. NCAC does not endorse products that are featured in this column. Information is provided to keep readers abreast of the latest prod-ucts industry has to offer.[NTS].

Walls with higher sound trans-mission class (STC) val-ues have been achieved for

years using a variety of construction techniques. Unfortunately, the proposed methods have involved a greater wall depth, a highly trained labor force, or both. A widely recognized technique is that of a resilient mounting attached to the structural framing. This approach has been used in various forms from the 1960’s through today. When installed correctly, structural isolation typically improves STC ratings by about 6-12 points, depending on the base construc-tion. Unfortunately, proper installation of these systems is complicated and time intensive. The result is too often an ex-pensive failure. A family of new acoustical wall ma-terials is Quiet Solution’s QuietRock, a constrained layer damped gypsum board. The primary application for these products is as a drywall replacement in multi-family residential dwellings where acoustical isolation is critical. QuietRock looks and works like traditional materi-als. The only difference is that it contains sound deadening viscoelastic polymers in several layers inside the panel. The damped layers are forced into shear by the stud framing. Of particular interest to acoustical consultants and architects is the suggested sound rated partitions are supported with the best available test data and realistic assessments of installed cost. One major advantage of QuietRock is the ability to use standard construc-tion techniques and still achieve high STC ratings, without the limitations found with traditional materials. Qui-etRock panels can be cut and attached to the frame just like drywall. Such an approach has several advantages over

Manufacturer’s Cornerresilient systems. For example, the wall system does not consume the additional fl oor space required by isolation clips. This is also the fi rst technology for walls that cannot be short-circuited via adja-cent structures (walls or outlets) or fas-teners such as screws or nails. The walls are not fl oating so additional skilled labor is unnecessary. Elimination of these elements results in a fewer post-construc-tion litigation concerns for architects and building owners.

QuietRock comes in several performance grades and vari-ous panel sizes. The panel best suited for typical multi-family applications is QR-530. It is 5/8 inch thick and has a weight similar to regular drywall. It is approved for use in various 1 hour fi re-rated as-semblies listed by UL.

The following drawing details compare the cost and performance of various wall systems. All of the acoustical test results are taken from referenced Canadian National Research Council (NRC) test reports. Full reports and product litera-ture are available for download from the Quiet Solution website (www.quietsolu-tion.com)

Comparing the performance and cost of several single layer stud wall assemblies, one fi nds:

STANDARD SINGLE STUD WALLTYPE X GYPSUM ON BOTH SIDES, WOOD STUD CONSTRUCTIONSTC:34 TEST NUMBER: NRC TL-93-157

NO EXCUSE WALLQR-530 ON ONE SIDE, TYPE X GYPSUM ON THE OTHER, WOOD STUD CONSTRUCTIONSTC:52 TOTAL INSTALLED COST: $5.89 / SFTEST REPORT: NRC B3414.5

SINGLE STUD WALL w/ RESILIENT CHANNELTYPE X GYPSUM ON BOTH SIDES, WOOD STUD CONSTRUCTIONSTC:46 TOTAL INSTALLED COST: $6.39 / SFTEST NUMBER: NRC TL-93-156

Quiet Solution is also pleased to an-nounce the highest acoustical rated double stud wall commercially available. This groundbreaking partition outper-forms the STC-66 possible with standard gypsum wall and uses the same standard construction techniques.

HIGHEST STC WALLTWO LAYERS OF QR-530 ON BOTH SIDES,DOUBLE WOOD STUD CONSTRUCTIONSTC:74 TEST REPORT: NRC B3414.2

Independent fi eld acoustical test reports show similar performance to those mea-sured in the lab and do not require the traditional 5 dB “fi eld reduction”.

QuietRock panels are available nation-wide through local dealers.


By Red Wetherill, Consultant in Acoustics, Alameda, CA

Editor’s Note: The author served as a senior consultant with the fi rm Shen Mil-som & Wilke/Paoletti; during the period when consulting services were initiated on this project [NTS]

Saint Martin’s Episcopal Church is in many ways exceptional in that it returns to an architectural form

dating from a time when acoustical re-quirements were dramatically different from the present day. The acoustical goal defi ned for Saint Martin’s was to com-bine support for choir, organ and other instruments with congregational singing and intelligibility of the spoken word. The cruciform plan places the 80 rank, 4 manual Schoenstein pipe organ optimally at the east end, speaking over the choir along the wider than traditional nave. The gothic vaulted ceiling is high enough for a mid-frequency reverbera-tion time of over 3 s with full congrega-tion, while pew-seat cushions control excessive reverberation for small gather-ings. On the basis of design calculations, a spray-on sound absorbing material was installed on selected vaulting surfaces, with the later addition of a limited area low on the transept walls for control of cross-room echoes.

Figure 1. View of the chancel platform

Saint Martin’s Episcopal Church, Houston, TXshowing the Schoenstein pipe organ.

The design goal entailed isolation from nearby heavy traffi c, occasional aircraft fl y-overs and control of noise and vibra-tion from the air conditioning system – a necessity for much of the year in Hous-ton’s climate. Double-glazing for control of traffi c noise was recommended only for the balcony but a complete installa-tion of stained glass provides double-glazing with a 1 inch air cavity through-out. Fan equipment is remote from the sanctuary, and duct layout was developed with the system designer to ensure that the large volume of conditioned air need-ed for a full congregation in midsummer could be distributed over the seating area without exceeding the noise criterion of NC-25. Airfl ow noise at diffusers was verifi ed in laboratory tests during the de-sign process. The challenge of attaining intelligi-ble speech in a reverberant space was re-solved by the use of digitally-controlled loudspeaker arrays [Editor’s Note: Duran Audio Intellivox loudspeakers] whose slenderness allowed for conceal-ment in the main structural piers on each side of the chancel. One is located on each side at the front of the chancel, so we asked the architect to consider hous-ing them within the two main piers (i.e., the compound columns that support one side of the major vault where the tran-septs intercept the nave). The piers are structural steel within a plaster enclosure having the traditional form of the Gothic pier. Since in plan the loudspeaker would fi t within the width of one of the circular “lobes” of the pier, the architect came up with a fi ne mesh surface to cover it, and he did a superb job of getting it to match the plaster sections on each side. The front-center lobe of each pier hides the loudspeaker array. The sound-transpar-ent covering matches the color and form

of the piers so well that it is impossible to distinguish from a distance of several feet. Other loudspeakers at the baptismal font and serving the choir are similarly installed.

Figure 2. View of one of the piers showing the sound-transparent cover-ing over the loudspeaker (fourth lobe from railing).

The organ builder encouraged close collaboration in the acoustical design and has expressed satisfaction with the outcome. Special thanks go also to the Church, architects Jackson & Ryan, many other disciplines, and colleagues John Prohs and Chris Papadimos at the San Francisco offi ce of Shen Milsom & Wilke. In the fi nal analysis, it is due to the continued attentiveness of the archi-tect and the design and construction team that the acoustical design goal has been fulfi lled.

Loudspeaker


By Peter AllenNCAC Executive Directors

The following summarizes ad-ditional items not addressed by NCAC President Ed Logsdon in

his “President’s Message” that resulted from the Board of Director’s 15May 2005meeting. Professional Liability Insurance – President Logsdon investigated a pos-sible group plan with CNA, but premium rates are different, not cheaper for each member fi rm. Professional liability insur-ance will be left to individual member fi rms to determine coverage. LRPC Report – Chairman Tony Hoover summarized the 14 May 2005 meeting. Under Old Business, the LRPC discussed the Financial Review, News-letter Advertising Policy, Branch Offi ce

NCAC Board of Director’s 15 May 2005 Meeting Directory listings, the Oregon Registra-tion issue, acoustical consulting vs. audio visual fi rms, fi rm ownership changes, use of “acoustical consultant” designa-tion, and an update on the Acoustics.com website. Under New Business, the Manage-ment Review Commit-tee will seek proposals from various soci-ety management fi rms. Board Member Jack Randorff will update the Policies & Procedures Manual in preparation for putting it on the website. The LRPC Committee referred to the Marketing Committee a recommendation to hire a publicist, reviewed and confi rmed the current policy on product sales as be-ing adequate, and agreed that interesting

business seminars should be announced earlier to encourage greater meeting at-tendance.

AIA Convention Exhibit – The board discussed a possible booth or hospitality suite at the next AIA convention. Board Member Dave Marsh will investigate further. Certifi cation of Acoustical Consul-tants – INCE will survey its members about Certifi cation. NCAC will monitor INCE’s progress.


Editor’s Note: Part 2 of the consult-ing advice article that appeared in the Spring 2005 Newsletter follows below. The fi nal article will appear in the Fall 2005 Newsletter. A book on the history of consulting at BBN edited by Eric Wood which includes these “advice” essays is in press. Contact Eric at [email protected] for publishing information. [NTS]

From Jack Curtis

1. One should develop the ability to write good letters and project reports that clearly set forth the consultant’s thoughts and recommendations. Most good con-sultants never hesitate to have their drafted letters reviewed by colleagues to be certain that they are clearly written. If a colleague doesn’t clearly understand what you are trying to say, surely a client will have a problem, too. Even someone like Bob Newman, an excellent writer, would often turn to others for their com-ments on one of his letters. Writing a re-port using clear and simple English is no easy task and since it is usually the main product that the client is paying for, it must be done well.

2. Clients’ telephone calls and letters must be answered, fairly promptly – and if that cannot be done, the client should be told why a prompt response may not be possible and when he can expect to have a response. For a client, being told of a valid reason for a delay is often ad-equate. It is surely preferable to a tardy response from a consultant, when a time-ly response was probably anticipated. Always keep a client well informed.

3. When it is predicted that fees will be higher than predicted, the client must be one of the fi rst to know. The reasons may be completely acceptable, whereas expenditures that have already exceeded expectations will be hard to swallow by any client, after the expenditures have already been made.

4. Always make fi le notes about any conference or telephone conversa-tions that will back up discussions and agreements that have not been made in

Acoustical Consulting Advice Series – Part 2writing. Even messily scribbled notes (dated!) will often suffi ce to clarify a situation, sometime in the future.

5. During the course of a project, even brief contacts with a client, to keep them well informed about the progress of your work will often keep them happy, if there is no other way that they will know what you are doing on the project. So many times, problems in consulting relation-ships could easily have been avoided by timely contacts with an anxious client. Remember that, beyond the provision of good professional services, you want to do your best to encourage a client to look forward to coming back to you, the next time he needs your services.

6. In a way, it all comes down to being responsible, by keeping the client well informed as the consulting project moves ahead. Let there be no surprises!

Editor’s Note: Please see obituary re-membering our late colleague in the Spring 2005 newsletter. [NTS]

From David Keast

Consultants have a bad reputation: wit-ness Dilbert. This is because some of them do not know enough about what they are consulting on, some want to make a fast buck and run, some want to lock in the client so he has to increase the budget or fund the add-on project. Of course, most really want to do a good job. One of the things I respected about BBN was that the unwritten company motto was “Solve the Problem” (quickly and at minimum cost, of course). When The Big Boss came into your offi ce it usually wasn’t to ask about your charge-ability; it was to ask about what you were working on. This would frequently lead to The Boss’s technical suggestions for your project. He was really interested in what you were doing and he wanted to help. Maybe this refl ected the academic

background of the place. The point was, the client was paying us to solve a prob-lem, not to maximize the return to BBN. Hopefully the marketplace would reward doing the best job. Of course, this was before Microsoft trounced Apple.

So I think that what makes an excel-lent consultant is that he focuses on solv-ing the client’s problem. He approaches the problem like (an old-fashioned) phy-sician. He is honest in his dealings with his client. If he needs help he pays for it. If he thinks he cannot do it he recom-mends someone else who can.

One of the nice things about acoustical consulting is that it is a small pond. The fi eld is served by many individuals and small businesses that are free to concen-trate on solving their clients’ problems with a minimum of distraction by issues of business growth, fi nance, personnel and the like. No great empires will be built in acoustical consulting. No Wall Street; MBA’s scurry elsewhere. Tort lawyers can’t be bothered. As a result, acoustical consulting can be really fun.

From Laymon Miller

Know your subject.

1. Express your recommendations in ordinary language, not scientifi c or tech-nical gobble-de-gook.

2. Write clearly and unambiguously, with adequate explanation and descrip-tion (in words, fi gures, charts, drawings, illustrations, etc.). The client relies more on what you write than what you say.

3. Answer the questions that befuddle the problem.

4. Consulting includes teaching: Teach Continues on page 13


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the client enough about the “what”, “why”, and “how” of the acoustic deci-sion or reasoning, so that the client can make informed decisions when the con-sultant is not present. If the explanations get too long, offer a preface that summa-rizes the results (“Executive Summary”).

5. Meet the deadline and the cost esti-mate that have been agreed upon. A late report may lose its value for an immedi-ate problem, and a serious over-run in cost leaves a bad taste. If either of these is going to happen, it is best to advise the client in advance.

6. Avoid giving snap judgments at the site or at fi rst impulse. With time to think, a better solution may develop.

7. Maintain strict confi dentiality of the

client’s interests and proprietary informa-tion.

The above list might be summarized with the slogan that I saw in a shoe re-pair shop in New York City back in the 1960s: “The Quality of a Job Well-done will be remembered long after the Price is Forgotten”.

From Carl Rosenberg

Have a passion for consulting. It is more than just engineering.

1. We have to provide our clients with the confi dence that we have the ability to fi x their problems and reduce their risks, not just some numbers in a report.

2. We have to understanding the broad implications of proposed solutions, not just the separate engineering tasks.

Acoustical Consulting Advice Series 3. We have to work closely with people and interact with teams, not just solve a strictly technical part of the work.

4. We have to juggle a lot of activi-ties at once and handle multiple tasks, not just focus on one task. When in the middle of one project, questions from another project will invariably arise and require an interruption from whatever you are doing, and will require an answer right away.

5. And we have to be able to communi-cate in a lucid, clear manner, even when the issues may be quite complex and far from simple.

Consulting is not for everyone, but for some people this passion provides a life-time of rewards and fulfi llment.



By Les Blomberg, Noise Pollution Clearinghouse

Editor’s Note: Les Blomberg is Executive Director of the Noise Pollution Clear-inghouse, a national non-profi t based in Montpelier, Vermont engaged in protect-ing Peace and Quiet. Website: www.no-noise.org. [NTS]

Quiet Please!

Road traffi c, jet planes, jet skis, garbage trucks, construction equipment, car alarms, lawn

mowers, leaf blowers, boom boxes. The world has gotten too noisy! Noise is aural litter – audible trash. Noise is to the soundscape as litter is to the landscape. The textbooks have it wrong. Noise is not unwanted sound; noise experts do not measure unwanted sound. There isn’t a noise meter invented that measures people’s wants and de-sires. Noise experts measure, and noise is, a pollutant. It is the most pervasive pollutant today, and there is little escap-ing it – not in the suburbs, not in the rural countryside, and not even in our National Parks. Noise has been a problem for thou-sands of years. Perhaps the fi rst inter-est in noise came not from people, but from the gods. According to the Epic of Gilgamesh, the earliest version of the Biblical fl ood story, humans were all but exterminated because the uproar of mankind made sleep impossible. More

Guest Editorialrecently, Caesar banned chariots from Rome at night so people could sleep, and even more recently, the Swiss banned airplanes at night for the same reason. In the United States, we have been less inclined to use regulation. To protect ourselves from noise, we have turned our backs on our neighbors, choosing back-yard decks over front porches, sound walls over sidewalks, and rural and sub-urban development over more sustain-able and densely populated villages and cities. Yet, rural and suburban sprawl, as a solution to noise pollution, is not work-ing. Noise continues to grow, particular-ly in places once considered quiet. The result is that noise, according to the U.S. Census, ranks higher than crime, traffi c, and poor public services as a cause of popular dissatisfaction with neighbor-hoods. The Noise Pollution Clearinghouse (NPC) is a national non-profi t, formed in response to the growing noise prob-lem. The mission of NPC is to create more livable cities and more natural rural and wilderness areas by reducing noise pollution at the source. NPC is trying to protect and increase opportunities for Peace and Quiet, and perhaps to save the world (remember The Epic of Gilgamesh – it wasn’t until we started burning fossil fuels that people really started to make a racket – the gods can’t be happy). NPC is part library, part reference librarian, part research institution, and part advocate for Peace and Quiet. NPC is helping individuals, organizations, and communities quiet their environment. The message of the Noise Pollu-tion Clearinghouse is that the world does not have to be as loud as it is. Peace and Quiet are not impossible in a technologi-cally advanced society; most noise is the result of technology, but technology can also quiet noise sources. NPC’s offi ce is cluttered with the results of testing to fi nd quiet products. To reach the staff you must walk over, or on good days, around, quiet lawn mow-ers, alternatives to leaf blowers, and even quiet chainsaws. This year NPC is busy identifying and promoting the quietest lawn equipment, including mowers, til-lers, trimmers, and saws. Next year we

expect to be surrounded by quiet air-con-ditioners and computers. The results of NPC’s noise tests are attracting the attention of manufactur-ers who are building quieter equipment, consumers who are purchasing quieter equipment, and the media who are cov-ering both. In the past year NPC and its message have been on the front page of USA Today, and in the Los Angeles Times, New York Times, Christian Sci-ence Monitor, Boston Globe, Washing-ton Post, Wall Street Journal, as well as Backpacker Magazine (where NPC picked the quietest spot in America) and half a dozen other magazines. The 20th Century was the noisiest one ever. The 21st Century could easily surpass it – we have the technology. But it could also be quieter – we have the technology for that too. In the 21st Cen-tury, I think people will choose the nice house in the quiet neighborhood over the nice house in the noisy neighborhood, the quiet refrigerator over the noisy refrigerator, the quiet washer over the noisy one, and so on. My bet is that no one really wants to announce to every-one in their house that they just fl ushed the toilet, and that no one really wants the entire neighborhood to know they are mowing their yard. But more impor-tantly, our goal is that in the 21st Century, we move beyond subjective wants and desires to treat noise as an objective pol-lutant that should be reduced.


Carl graduated college (Princeton) in 1965 and started on the road to his career dream of becoming

an architect by attending M.I.T. School of Architecture. His path toward that goal was interrupted by Uncle Sam (Carl was drafted and served in the Army for two years) and by the realization that acoustics, as taught at M.I.T. by Bob Newman, was more of a calling than de-signing buildings. The course that Bob taught was exciting and compelling, and acoustics drew on Carl’s interest in mu-sic and building technology. After graduating from M.I.T. in 1971, he joined the staff of Bolt Beranek and Newman BBN in Cambridge, MA. Under guidance from Bob Newman, Jack Curtis, Parker Hirtle, Ted Schultz, Charlie Salter, and many others, Carl had the opportunity to work on a wide variety of projects, from performance spaces, to equipment noise monitor-ing, community noise problems, room acoustics, and sound isolation issues. The diversity of projects and the sup-port from BBN’s outstanding staff made these years a wonderful time of challeng-es and growth. Over time, Carl assumed increased managerial responsibilities and became the manager for the architec-tural acoustics group. At the same time, BBN grew into a large, publicly owned company with extensive research and development work for the government (on everything from underwater acous-tics to packet-switching technology). In 1989, BBN reformed the Architectural Acoustics and Environmental Technolo-gies division into a separate company,

Acentech. Two years later, Carl and other senior colleagues purchased this com-pany and Acentech reverted to an em-ployee-owned consulting company, with primary focus on architectural acoustics, sound and audiovisual systems design, and environmental noise control. In 1978, Ranger Farrell, who had been an innovative consultant at BBN years before, was incapacitated and un-able to complete his responsibilities teaching a course in Architectural Acous-tics at the Princeton University School of Architecture. The dean of the school asked Bob Newman to help out, and Bob and Carl jointly taught the acous-tics course at Princeton for a few years. By 1981, Carl had assumed the primary teaching role, and has taught at Princeton since then. After Bob Newman passed away suddenly in 1983, Carl also fi lled his mentor’s shoes at M.I.T., teaching Continues on page 18

Members In The Newsthe same course that had inspired Carl’s interest in acoustics 18 years before. For the past several years, Carl has also taught a similar course at Washington University in St. Louis, MO. The opportunity to teach architec-tural acoustics and to participate towards accomplishing the objectives of the Robert Bradford Newman Student Fund programs is a source of great satisfaction and honor for Carl. He has served as co-chair of the Newman along with Bill Ca-vanaugh since the outset of the Newman-Fund following Bob Newman’s death in 1983 and coordinates the Theodore John Schultz Teaching Grants awarded by the Fund biannually as well as in the award of Newman Medals to students for “excellence in the study of architectur-al acoustics” at universities throughout the world and in the award of Wenger

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Everything Acoustic!In 1992, RPG developed the Variable Acoustic Modular Performance

Shell. Since then, VAMPS® has been successfully used in prestigious

performance facilities all across the country. Most recently at the

Orpheum Theater,in Phoenix,AZ. As part of RPG’s Next Generation effort,

we have developed completely new rollable and fully flown acoustical

shell towers and canopy systems,called Overture™.The flown system can be rigged,using conventional counter

weights or the Vortek® remotely controlled,computerized hoist system. We have also developed new composite,

damped materials for the facade, which offer a rigid, damped and lightweight surface. We invite you to inquire about the specification,

implementation and performance details and request a free animation of this exciting new product. This is only the beginning.............

DIFFUSE NEWS

Volume 10, Issue 3, 2005The Newsletter for Progressive Acoustics Research

“While attempting to achieve uniform

coverage, most commercial acoustical

shells have limited diffusivity. RPG is

proud to announce a new generation of

rollable and flown acoustical shells, based

on RPG’s patented Aperiodic Modulation

of a Single Asymmetric Base Shape™.”

1. Diffuse News

Overture™: The Next Acoustical Shell

2. Research & Development

The Forgotten Octave

Dr. Peter D’AntonioPresident and CEO

RPG is proud to announce Overture™: TheNext Generation of Acoustical Shells andCanopies, using RPG’s patented Aperiodic

Modulation of a Single OptimizedAsymmetric Base Shape™

Overture™

©2005, RPG DIFFUSOR SYSTEMS INC.

®

For up to the minute information, we invite you

to visit RPG’s acclaimed web site:http://www.rpginc.com.

IN THIS ISSUE CONTINUALLY EVOLVING......

OVERTURE: THE NEXT ACOUSTICAL SHELLMost commercial acoustical shells are formed from simple,

periodic arcs. We have created a white paper available at

www.rpginc.com/whitepapers/waveform.pdf, which

explains the limitations of this approach. Simply stated,

periodicity produces grating lobes, which constrain the scat-

tered energy in a limited number of diffraction directions,

regardless of the uniform scattering capabilities of the

repeat unit. While attempting to achieve uniform coverage,

most commercial acoustical shells have limited diffusivity.

RPG is proud to announce a new generation of rollable and

flown acoustical shells, based on RPG’s patented Aperiodic

Modulation of a Single Asymmetric Base Shape™. The new

Overture Shell, consisting of overhead canopy elements, rear

wall and side towers, is offered in two options: rollable coun-

terweighted towers and flown canopies and a fully rigged

and flown system, illustrated in the Figures at the right. The

flown system can be rigged with conventional counter-

weighted systems or remotely controlled, using the Vortek®

automated hoist rigging system. The shell facade is fabri-

cated from a new damped, lightweight, wood or fiber-rein-

forced gypsum composite. Several systems are in produc-

tion and we look forward to describing this new

Performance System to the acoustical community.

Figure 1. Overture in stored flown position (Two sidetowers not fully flown for clarity). Canopy, rear wall andside towers store parallel to battens.

Figure 2. Overture in play position. Canopy elements arelowered and tilted. Rear wall is lowered. Side towers arelowered and rotated into position. Access doors are open.

63 125 250 500 1k 2k 4k 8k 16k-30

-20

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ssure

leve

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63 125 250 500 1k 2k 4k 8k 16k20

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31.5 63 125 250 500 1000 2000 4000 8000

H


Our shallow (4”) Modex™ Plate and Broadband, along

with the room dimensional optimization software, Room

Sizer™, virtually eliminate modal effects in small rooms.

Let’s look at the benefits that can be derived for speech

intelligibility and music fidelity.

The spectra for male and female speech are shown in Figure 1.

Maximum speech energy is contained in the 250 and 500 Hz octave

bands and 75% of speech intelligibility is contributed by the 1 - 4 kHz

octaves. It was thought that energy below 125 Hz contributes little

to speech intelligibility, so most of the initial effort to improve speech

intelligibility focused on the high frequency intelligibility bands.

However, there is recent evidence by the Fraunhofer Institute that

low frequency reverberant energy, which can be significantly empha-

sized by room modes, causing amplification of more than 20 dB,

tends to alter the timbre of speech and psychoacoustically mask

higher frequencies, thereby interfering with intelligibility.The Speech

Interference Level, which is the numerical average of the sound pres-

sure levels of the background noise in a room within the 500, 1000,

2000 and 4000 Hz octave bands, ignores the noise levels in the lower

octaves. Now that the Modex™ Plate and Broadband are available,

recent observations have shown that controlling the octave bands

below 500 Hz,has a profound masking effect on speech intelligibility.

Another interesting effect observed when controlling low frequen-

cies is that speech levels tend to drop, as there is less of a reason to

raise one’s voice to compensate for interference, as described in the

Lombard effect. These findings may help reduce the use of artificial

noise masking approaches, which can only treat the symptoms and

not the cause. Thus, by decreasing low frequency reverberation, we

simultaneously lower background noise to reduce the masking of

intelligibility and lower conversation loudness levels to improve

speech privacy in open space environments.

Controlling low frequency interference can improve the learning

process in classrooms and lecture halls. A recent international com-

parative trial of student performance in reading comprehension, cal-

culus and natural science called PISA (Programme for International

Student Assessment) ranked the United States in the middle of the

group. While there are many factors contributing to this poor perfor-

mance, acoustics is clearly one of them. Much effort is now being

directed at improving the acoustics in learning environments and we

suggest including attention to the Forgotten Octave. In Figure 3,

we show the improvement in the reverberation time of a

small room in which 23 m2 has been applied to the ceiling

corners, behind a suspended absorptive ceiling. The ben-

efit to small rooms like recording control rooms (Figure

4), broadcast studios, musical rehearsal rooms, band

rooms, choral rooms, orchestra pits and home theaters is

clearly obvious, yielding low frequency extension

without the modal effects of boominess and excessive

decays.

In addition to small rooms, low frequency absorption can

improve large performance auditoria. Traditionally

folded velour drapery is used to provide variable

acoustics. However, the absorption characteristics of

drapery is not ideal, providing more high frequency

absorption than low. Modex panels can be attached to

rollable tracks and inserted as needed to control rever-

beration in the frequency band of interest.

In conclusion, the ability to extend effective absorption

down into the Forgotten 63 - 125 Hz octave with the

Modex™ Plate and Broadband offers a level of control

previously not available in small and large rooms.

Research & Development

BASS MANAGEMENT

®

Everything Acoustic!

63 125 250 500 1k 2k 4k 8k 16k-30

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)B

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Reve

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Reve

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Tim

e[s

]

Figure 1. Speech spectrum for a male (dark line) andfemale (light line) voice.

Figure 2. Determining a Speech Interference Level(SIL) from an external noise

Figure 3. Reverberation time measured in a smallroom before (open circles) and after (closed circles)application of 23 m2 of Modex Plate.

Figure 4. Reverberation time before (thin line) andafter (thick line) in a mastering control room. Upper(dots) and lower (dashes) refer to the ITU recommen-dations.


Continued from page 15Awards for winners of the ASA/TCAA Student Design Competitions. In 1995 Carl became President of Acentech Inc. (successor to the consulting division of BBN), and held that post until 2004. He is now a Principal consultant at Acen-tech, a Fellow of the Acoustical Society of America, and a member of the Nation-al Council of Acoustical Consultants. He continues to teach acoustics, and enjoys the vitality and interest and technical skills that students today acquire. [NTS]

Bennett Brooks New ASA Fellow

Bennett M. Brooks was elected Fellow of the Acoustical Society of America at the Spring 2005

Acoustical Society of America Meeting for “…contributions to noise control en-gineering, standards, and noise policy.”

The Council extends congratulations to Bennett on his election and recogni-tion for his contributions by colleagues and peers. [NTS]

Members In The NewsHoover Named to Acoustics Today Editorial Board

The NCAC Newsletter has learned that NCAC Immediate Past Pres-ident, Tony Hoover, has been ap-

pointed to the Editorial Board of the new Acoustical Society of America quarterly magazine, Acoustics Today. The fi rst issue of the full-color, quar-terly print publication is expected this fall. Tony and the other Editorial Board members are currently reviewing articles submitted for the premier issue. Acous-tics Today will provide technical and Society information, including techni-cal articles, tutorials, highlights of ASA committees, and other timely informa-tion of interest to the acoustical commu-nity.

Continues on page 19


Members In The NewsContinued from page 18

The Society’s fi nal issue of its highly successful newsletter Echoes will be in-corporated in the initial issue of Acous-tics Today, and its content melded into subsequent issues of Acoustics Today. The Society is currently search-ing for an editor for the new publica-tion. ASA Past-President Richard Stern is serving as interim editor until the new editor is selected. Candidates for editor should submit a cover letter describing their interest in and qualifi cations for the position, curriculum vitae/resume, and the names and contact information of at least three references. Nominations of individuals you may feel are qualifi ed are also welcome. All applications and nominations should be sent by e-mail or postal mail to: Judy R. Dubno, Ph.D.

Chair, Search Committee, Editor of Acoustics TodayAcoustical Society of AmericaSuite 1NO1, 2 Huntington QuadrangleMelville, New York 11747-4502E-mail: [email protected]

Review of applications and nomina-tions will begin in September 2005 and continue until the position is fi lled. The Offi cers and Members of the Council congratulate Tony on his selec-tion to this important and challenging position on the Editorial Board of Acous-tics Today. We are certain he can count on members of the consulting commu-nity and his many friends and colleagues throughout the acoustical community for their comments and contributions to this exciting new publication. [WJC]


By Ed Logsdon and Neil Thompson Shade

The technical session of the Spring 2005 NCAC presented a tutorial and demonstration of acousti-

cal modeling programs for environmen-tal noise and sound insulation by several competing manufacturers. The environmental noise programs included CadnaA and SoundPLAN. The sound insulation programs included BASTIAN and INSUL. The CadnaA and BASTIAN pro-grams were developed by DataKustik in Germany (www.datakustik.de), with U.S. representation by Scantek (www.scantek-inc.com). SoundPLAN is a German pro-gram developed by SoundPLAN (www.soundplan.com) and INSUL (www.insul.co.nz) was developed by Keith Ballaugh of Marshall Day Associates in New Zea-land. The latter two programs are repre-sented in the U.S. by Navcon Engineer-ing Network (www.navcon.com). Outlined below is a brief summary of the features of each program as pre-sented by their respective representa-tives. Please consult the manufacturer’s website or the U.S. representative for ad-ditional technical information and dem-onstration discs.

CadnaA1. Uses dynamic ray projection, not regular rays to avoid errors from gaps being missed by evenly distributed rays.2. Accuracy in prediction using stan-dard deviations to validate predictions.3. Modular, can add new areas to exist-ing maps.4. Modeling can fi t roads to ground contours and vice versa.5. Can simulate low sound power and intensity measurements.6. Has a library of special source emis-sions.7. Allows Excel spreadsheet input of source directivity charts.8. Can identify wind information, per-centage times, and direction.9. Can create a movie of a site walk-through for public presentation.

NCAC Meeting Technical Session Acoustics Computer Modeling Programs

10. Common database tracking all calcu-lations.11. Can enter equations such as sine wave to defi ne ground contour shapes.12. Can import bitmap (.bmp) fi les.

SoundPLAN1. Can produce 3D predictions for public address systems based on directivity data for loudspeakers.2. Uses point and area sources.3. Allows tiling of models and calculations.4. Global setting & templates for proj-ects.5. Can provide Leq, L90, and L10 predictions as well as Day0, Evening5, Night10, or Day-Night time periods.6. Considers source annoyance, such as railway vs. car horn.7. Calculation history is stored in spreadsheet along with a log of work.8. The software defi nes “situations” that contain geographic data with identi-fying characteristics of areas being cal-culated.9. Can stop/start prediction calculations and also can recalculate specifi c areas.10. Allows “If then else” logical equa-tions.11. Can defi ne road surface by traffi c count and speeds along the road but still treats information as a single object.12. Can import traffi c count data from Excel spreadsheets.

BASTIAN1. Includes direct and sound fl anking transmission paths in predictions, i.e., up/down, horizontal, and outside/inside.2. Transmission loss data for several hundred constructions.3. Can export drawing as .dxf fi les.4. Compares direct vs. sound fl anking contributions.5. Can enter actual windows and wall panels.6. Can import information to CadnaA.

INSUL 1. Can use either metric or imperial units for dimensions.2. Predicts STC and OITC from trans-mission loss data.3. Can handle orthotropic panels that

have different stiffness in X and Y direc-tions.4. Calculations are based on mass law, coincidence effect, using Sharp’s equa-tions.5. Transmission loss accounts for panel size (Sewell’s correction).6. The panel radiating area is defi ned as the area between the studs for a single panel.7. Density, stiffness (Young’s modu-lus), and damping (usually estimated) are used for calculations.8. Has material database in .txt fi le that the user can edit or create new materials.9. Has absorption database in .txt fi le with thickness and fl ow resistance.10. Typical prediction accuracy within +/- 2 dB.11. Metal stud predictions good up to 20 gauge studs.12. Latest version has added IIC predic-tions for concrete fl oor slabs.

Editor’s comments: Having “demo-ed” all of the above programs, and after purchasing two of them, potential us-ers should plan on considerable time to learn the program conventions and to understand the program’s features and quirks. Overall, once the initial learning curve is somewhat mastered, you won-der why you did things by spreadsheet or manual calculation for so long. For many of us, including myself, “old habits die hard.” [NTS].


The Acoustical Society of America is cosponsoring an international and interdisciplinary research

conference entitled, “Aging and Speech Communication,” to be held at Indiana University, Bloomington, Indiana, from 9-12 October 2005. The basic idea behind the confer-ence is to bring together audiologists and hearing scientists who are doing research on “bottom-up” processing in the area of speech communication in older adults with psychologists and cognitive scien-tists working on the same problem, but largely from a “top-down” perspective. It is hoped that exchanging information from both perspectives will lead to a bet-

Special Meeting Announcement Aging and Speech Communication

ter understanding of the speech-com-munication problems of older adults, as well as to improved approaches to mini-mizing those prob-lems. The conference website provides complete details and can be found at: http://www.indiana.edu/~ascpost/index.htm Scholarships covering conference and travel costs are available for several pre-doctoral and post-doctoral appoin-tees submitting posters.

Editor’s Note: Thanks to Maureen Stone, Chair of the ASA Technical Committee

on Speech Communication and Elizabeth Strickland, Chair ASA Technical Com-mittee on Psychological and Physiologi-cal Acoustics for submitting this notice. [NTS]


By Laymon N. Miller, Hon. NCAC, Contributing EditorEmail: [email protected]

Author’s Note: This was written after attending an earlier Acoustical Soci-ety Meeting. Is it still timely? You be the judge. Maybe your children or grand-children should read it and decide if it applies. [LM]

It may seem like fun to listen to loud music; maybe you believe you actu-ally enjoy it that way. Then, would

you listen to this: You will not enjoy the permanent loss of hearing that inevitably will follow long periods of hearing loud sounds. A hearing aid for the rest of your life is not that much fun. We as a nation would be frightened and appalled if we were told that there is an unknown malicious, infectious, sinis-ter, medical epidemic among us – some-thing that would affect our own children and grandchildren. Not someone else’s, but our own. Not in some faraway coun-try, but right here at home. It is hard to believe, perhaps, that we are right now in the midst of just such an epidemic. A Task Force of the Acoustical So-ciety of America, at its 1994 meeting at MIT, had as one of its tasks the publicity of the seriousness of this intrusive threat to society. It is a natural tendency for an older population to slowly acquire a

It’s better than the alternative….Hearing is Fun; Don’t Lose It

hearing loss. There are a number of fac-tors involved and they all slowly work away on our hearing during our later years. But now, it is starting at much younger ages. High sound levels cause hearing loss! You do not have to operate a jackhammer all day or work in front of a noisy machine all day. Hours and hours of loud music, in your own room, played at sound levels of 100 to 120 decibels over a few years’ time will do it. It comes on so slowly: maybe only 2 or 3 or 4 decibels loss in a year. That is so small, we do not know the difference. In 5 to 8 years, though, that makes a big difference. It is not good, but we can get along with a 10 to 20 dB loss. However, a 30 to 40 dB loss is serious and places us at a real disadvantage. We have to ask people to speak louder, we fi nd telephone conversations diffi cult or impossible, we turn up the radio or TV so much that it is uncomfortable to others in the room, and we start thinking about getting a hearing aid. All of that is a pretty pitiful sequence for a young person. Also, a sad fact about noise-induced hearing loss is that it is permanent. When those nerve cells are destroyed, they do not grow back. We only get one set in a lifetime. We really must protect them. In earlier days of loud music, the performers themselves were losing their hearing, but they did not want to admit it. They feared that would turn people

away from their concerts. Now, they are beginning to admit it. Sure, a hearing aid will help, but there is nothing as good and convenient as our own undamaged ears for a lifetime of listening enjoyment. Just ask someone who is wearing a hear-ing aid. There is no longer a stigma to it; it just isn’t as good as your own unaided hearing. One audiologist at that 1994 meeting gave these statistics: (1) there is two to three times more hearing loss now than only ten years ago, (2) one study found that 60 percent of an incoming group of college students had a signifi cant amount of hearing loss, and (3) another study stated that 8 percent of a large randomly-selected group of younger people had serious hearing impairment. In any other disease, those numbers would be consid-ered of epidemic proportions! What to do about it? Turn down the volume control. The pathetic fact is that this warning and advice comes from the older generation, so it is likely to be ig-nored by the younger generation. You have to fi rst lose your hearing to ap-preciate how valuable it was. The hear-ing aid is an expensive and partial rem-edy but it is not a pleasant convenient solution to the problem. Please turn down the volume control: in 10 years you will be glad you did.

The Institute for Research in Con-struction (IRC), part of the Cana-dian National Research Council,

has two documents on speech security that may be of interest to NCAC mem-bers. IRC research has identifi ed three speech security levels: (1) Threshold of Intelligibility (below which speech is not intelligible), (2) Threshold of Cadence

(below which the rhythm or cadence of muffl ed speech is not audible), and (3) Threshold of Audibility (below which speech sounds are not audible). The IRC data are based on both sub-jective listening tests and acoustical mea-surements. The measurements include talker and in-room noise levels obtained during actual meetings and sound trans-mission measurements of typical interior

New Speech Security Documents Availableconstructions. The IRC reports are Number 170 “Speech and Noise Levels Associated with Meeting Rooms” and Number 171 “Measures for Assessing Architectural Speech Security”. The documents can be downloaded from http://irc.nrc-cnrc.gc.ca/fulltext/rr170 and http://irc.nrc-cnrc.gc.ca/fulltext/rr171. [NTS]


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By Noral Stewart, Ph.D2000-2002 NCAC Presidente-mail: [email protected]

A major revision of ASTM E336 in the works for the past seven years has been approved and

published. This revision is now THE standard effective immediately and con-tains several very signifi cant changes. Any measurements henceforward that must be in compliance with E336 must be in compliance with this new version. The new E336-05 is now available for download from ASTM and will be in the standards book when published in Oc-tober. The most signifi cant change affect-ing results is when noise reduction (NR) and noise isolation class (NIC) are to

be reported between rooms and either room is 150 cubic meters or larger. The revision in this case requires that mea-surements be made and averaged only in an area 1 to 2 meters from the divid-ing partition on each side, and not over the full room. When this procedure is used for large rooms, there is a new requirement to make sure the sound distribution over the partition on the source side is evenly distributed. Compared to the past methods, this means that the NR and NIC will be lower in cases where the receiving room is large and highly absorptive. The most common situation where this will occur is in the testing of

operable partitions. This change makes the NIC more dependent on the partition performance and less dependent on the room conditions. A new measure and rating has been

introduced, the apparent transmission loss (ATL) and apparent sound trans-mission class (ASTC). These apply to conditions as found with no attempt to eliminate structural sound fl anking. They

ASTM E336 Standard is Revised

Continues on page 24


intentionally include the sound fl ank-ing. Also, these measures are allowed in smaller rooms than are required for fi eld transmission loss (FTL) and fi eld sound transmission class (FSTC), as small as 25 cubic meters with the smallest dimen-sion at least 2.3 m. The maximum ab-sorption requirements are not imposed in rooms less than 150 cubic meters. These measures provide a way of reporting results that have often in the past been incorrectly reported as FTL and FSTC. Consideration was given to redefi ning FTL and FSTC, but this was strongly op-posed by Canadian voters who wanted all conditions of full fl anking, partial fl anking, and no fl anking clearly defi ned.The traditional requirements for measur-ing FTL and FSTC are more strongly emphasized, along with the requirement that results must be labeled “Minimum” unless it is proven that no sound fl anking exists. The method of evaluating sound fl anking is changed from covering the

test partition to covering all other sur-faces in the rooms. This is for two rea-sons. It was found that covering the test partition did not eliminate all fl anking, and doing so provided no way to actu-ally measure the FSTC when fl anking is present. In practice, in the future as in the past, most FTL and FSTC results should be labeled “Minimum.” Among many other minor changes, the following are the most signifi cant:1. The measurement of Normalized Noise Reduction (NNR) and Normalized Noise Isolation Class (NNIC) is limited to spaces in the range of 25 to 150 cubic meters with a minimum dimension of 2.3 m.2. Requirements for background noise measurement are clarifi ed.3. A requirement has been added to list all equipment used and the most recent laboratory calibration date for measure-ment equipment. 4. The new standard E2235 for mea-surement of sound absorption in spaces

is referenced rather than providing the details for this within E336.5. It is clarifi ed that rounding is to oc-cur after subtraction of the levels in the two rooms.6. A more specifi c description of the environment and partition is required in the report.7. A requirement is added that report pages containing results must be labeled as not constituting a complete report, and additional notes must be placed on those results pages if the test does not meet all requirements of the test method or if the results do not represent the normally ex-pected result. A future revision is expected to ad-dress an oversight that left discussion of the treatment of coupled spaces only in the annex covering FTL.

Editor’s Note: Thanks to Noral for pro-viding NCAC members a summary of the changes to this standard. Now to revise my spreadsheet….[NTS]

ASTM E336 Standard is RevisedContinued from page 23

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The Spring 2005 NCAC meeting presented “Honorary Member-ship” citations to three longtime

NCAC members: M. David Egan, P.E., Minoru Nagata, Ph.D., George Paul Wilson, Ph.D, all of whom have made signifi cant contributions to the acoustical consulting profession. David Egan is Professor Emeritus at Clemson University where he taught environmental science courses, including a 3 credit class in architectural acoustics to an estimated 4,000 students, many of whom are now active as practicing ar-chitects or acoustical consultants. David also taught at Tulane University, Geor-gia Institute of Technology, University of North Carolina, and Ball State Univer-sity. He has written seven textbooks on various environmental science topics, including his most popular textbook, Architectural Acoustics, published in 1972 and revised in 1988. As an acousti-cal consultant, David has consulted on roughly 900 projects, many with NCAC member fi rms. His projects have in-cluded most building types both in the United States and abroad. David is a graduate of Lafayette College and M.I.T. and is a Fellow of ASA and INCE Board Certifi ed. Other professional recognition includes Lifetime Nation Distinguished Professorship by Association of Colle-giate Schools of Architecture and Honor-ary Membership in the American Insti-tute of Architects. Minoru Nagata is founder, former President, and currently executive advi-sor of Nagata Acoustics, Inc., an acous-tical consulting fi rm he established in 1971. Dr. Nagata is a noted expert in auditorium acoustics, whose fi rm has designed many of Japan’s premier con-cert venues. Some of the notable halls include: Suntory Hall (1986), Tokyo Metropolitan Art Space (1990), Kyoto Concert Hall (1994), and Sapporo Con-cert Hall (1997). Prior to Nagata Acous-tics, he was a researcher at the NHK Technical Research Laboratory, part of the Japan Broadcasting Company. His work and NHK concentrated on acous-tic design of concert halls, broadcast and recording studios, and theaters. Between 1963 and 1964 he was a visiting re-searcher at Goettingen University (Ger-

many) studying European concert halls. Dr. Nagata has authored three books on architectural acoustics and is a gradu-ate of Tohoku and Tokyo Universities receiving a Bachelor of Technology and Ph.D. degrees. George Wilson formed Wilson, Ih-rig & Associates, Inc. in 1966, serving as fi rm President until 2003. He is an in-ternationally recognized authority in the areas of transportation noise and ground-borne vibration, where he pioneered vi-bration isolation technology to rail track installations. He has presented nearly 50 papers at acoustics and professional society conferences on topics relating to transportation noise, groundborne vi-bration transmission, building isolation, rail wheel/track noise and vibration, and

community noise. Wilson, Ihrig & Asso-ciates have consulted with many NCAC member fi rms to provide expertise in building vibration isolation, particularly those facilities, such as concert halls, re-quiring low noise levels. George is Past President of NCAC (1980 to 1982) and is a recipient of the Council’s C. Paul Boner Medal (1992). His education in-cludes B.S, M.S., and Ph.D. degrees, all from U.C. Berkeley. He was recognized for his contributions to acoustics and vi-bration consulting with an ASA Fellow-ship.

Editor’s Note: Biographies summarized from information provided by Bill Cava-naugh, Warren Blazier, Tony Hoover, and David Lubman. [NTS]

NCAC Honors Egan, Nagata and Wilson


Editor’s Note: Part 1 of this series ap-peared in the Spring 2005 newsletter.Part 2 of Eric Ungar’s verse and Jerry Garfi eld’s pictures addressing common topics in acoustics appears below. Stay tuned in subsequent issues for the con-cluding parts of the delightful Unger verses and Garfi eld illustrations. [NTS]

The membrane of the human EAR Responds to sound so we can hear.Its motion vibrates tiny bones,Wiggling small hair cells that sense tones.Their nerve cells connect to the brainFrom which information we gain.

The FREQUENCY of oscillationsTell us how many fl uctuations

Up and down from mean are reckonedPer unit time (minute or second).The unit “Hertz” is now preferred; Cycles-per-second has been interred.

G’s refer accelerationTo our earth’s own gravitation.Displacements may be very smallFor g’s aren’t small at all. And so, in many situations, Velocity’s used to mark vibrations.

Acoustics from A to Z – Part 2

The HEARING threshold, it is known, Is six dB for a pure tonePrecisely at 1000 HzAgreed upon by most experts.The smallest pressure we can hear?A billionth of an atmosphere.

Visit our website at

www.ncac.com


DENIS MILSOM 1942-2005Vice President, Shen Milsom & Wilke

Jeff Wilde, Partner, Shen Milsom & Wilke Denis Milsom passed away on Thursday 5 May 2005 following a brief illness. He was born in Liverpool, Eng-land on 17 December 1942. Denis started his professional career in the U.S. Army, serving in the United States and overseas. His education in-cluded graduation from the US Army Engineering School at Fort Belvoir, Vir-ginia. Denis started work at a New York acoustics fi rm in the late 1970s. There he met Fred Shen and the two became friends immediately. In January 1986, they formed their own acoustical con-sulting fi rm, Shen Milsom & Associates, Inc. The fi rm later expanded into audio-visual systems design and, after joining forces with Hubert Wilke, changed its name to Shen Milsom & Wilke, Inc., in 1988. A few of the hundreds of projects he worked on, and of which he was proud-est, are television studios for FOX, ABC, MTV, ESPN, and FX Cable; the New York Public Library Rose Read-ing Room, Bloomberg Headquarters, Goldman Sachs, Trump Tower, the Asia Society, and Viacom - all in New York City; numerous healthcare facilities, including Brigham & Women’s Hospi-tal, and Procter & Gamble Health Care Research Center; many Millennium Part-ners projects across the United States, the US Navy CINCPACFLT Fleet Brief-ing Room in Pearl Harbor, Hawaii, and the Yale University Art Gallery in New Haven, Conn. As an acoustician, Denis brought clarity of thought to the projects on which he worked. His ability to take on a sticky problem and fi nd a clean, clear, and practical way to solve it won him respect and support among the architects, engineers, developers, and contractors he worked with throughout the country. His effectiveness saved his clients money and time. As a member of the Acoustical So-ciety of America and former member of the Board of Directors of the National

Council of Acoustical Consultants, De-nis worked to better his profession. His offi ce walls contained certifi cates and badges from continuing education ses-sions he attended or chaired. All of these accomplishments are important, yet Denis was probably most admired for his calm, easy-going man-ner. He supervised dozens of projects simultaneously, managed a staff of tal-ented acousticians, and juggled work in Shen Milsom & Wilke’s multiple offi ces. Yet he never raised his voice, never had a confrontation, and consistently smoothed ruffl ed egos and frustrated clients with his soft voice and kind, gentlemanly manner. Denis mentored dozens of young people. “He always took the time to work through and explain, with seemingly little effort, the project issues that stumped the rest of us,” says one person who came to Shen Milsom & Wilke as a college grad-uate and has been with the fi rm for more than 15 years. Many of those he worked with have achieved success at Shen Mil-som & Wilke, at other fi rms, or at their own fi rms. Adds another associate: “It is not until someone like Denis leaves us that we realize how much he shaped us.”

[Council extends its condolences to the family and colleagues of Denis.]

CLIFFORD MICHAEL SROKA1941-2005President, CS Acoustical Engineering

Steve Pettyjohn, Principal, The Acoustics & Vibration Group

Clifford Michael Sroka, 63, passed away on Wednesday18 May 2005, at his home in Portland, Oregon. He suc-cumbed to chronic lymphocytic leukemia after treatment proved unsuccessful. Cliff was born 22 November 1941 in Chicago, Illinois. Cliff was an acoustical consultant for 32 years, spending the last 25 years with his company, CS Acoustical Engineer-ing, based in Portland. He worked with the Oregon Department of Environmen-tal Quality in his early days, helping to establish rules for acceptable noise expo-

In Remembrance

sure for residential property. He taught engineering classes at Portland State University and Portland Community College, mentoring many students. Cliff specialized in architectural acoustics and environmental noise control working on projects from Alaska to California and Oregon to Idaho. Cliff was a member of the Acoustical Society of America, the Institute of Noise Control Engineers and the National Council of Acoustical Con-sultants. Cliff was certifi ed by INCE in 1984. He worked out in a gym regularly to maintain his health. Cliff was an avid scuba diver, skier, bike rider, hiker and he loved riding horses in the mountains. He often rode the train to Seattle, enjoying the ride and the opportunity to relax away from his work. His love of trains led to many trips by rail through Europe, enjoying the food, especially in Italy. Survivors include his brother, Robert Henry Sroka, Chicago Illinois; sister, Dolores Sroka Lapinski, Midway, Georgia; one nephew, three nieces and many dear friends. An informal memorial services was held on 4 June 2005 in Creston Park in southeast Portland. In lieu of fl owers, contributions can be made to the Leu-kemia & Lymphoma Society, to Oregon Public Broadcasting or to a group of your choice.

[Council extends its condolences to the family and colleagues of Cliff.]

Denis Milsom


Most likely, the light refl ect-ed off me under a spotlight would be awfully dim, es-

pecially in comparison with my fellow NCAC board members, so I would like to use this column space to shine the spotlight on a few other folks instead. On 1 August 2005 will be the 10th an-niversary of Dohn and Associates, Inc. and I would like to highlight a few of the people who were instrumental in keeping the company afl oat during its fi rst years of business.

Rolly Brook: for his professional guidance and the huge pile of free offi ce equipment he gave me to open my fi rst offi ce. Doris Dohn: for the more than fi ve years of (virtually free) accounting services she provided. Gale Kordowski: for her moral (and fi nancial!) support.

Nick Roberts, David Tanza, Devendra Contractor, Ken Green, and Bob Har-ris: for their exceptional loyalty and ear-ly support of the company. Craig Park, John Pihl, Larry Myrick, and Keith Brummel: for their untiring efforts in keeping Dohn and Associates in busi-ness. Paul Landry, Jack Bogan, Rose Steele, and Heather McAvoy: for their personal and professional friendship. Joe Kucera, Ron Quillin, Tom Listmann, and Michael Gros: for their support, referrals, and camaraderie. Joel Lewitz and Bill Lightner: for their confi dence in the company and their willingness to collaborate on projects with Dohn and Associates. After nearly twenty years of acous-tical consulting and ten years of operat-ing Dohn and Associates, I have to say

that in terms of job satisfaction, running a business has been OK, consulting in acoustics has been good, and the people I’ve met have been great.

NCAC Director Spotlight: Bill Dohn Dohn, and Associates, Inc.


These Eckel facilities are ideal for acoustic testingand evaluation of • automotive and aerospacecomponents & systems • audio systems • loud-speakers • microphones • computers • appliances• consumer electronics • industrial components . . .as well as for identifying noise sources for productimprovement programs . . . and for research inacoustics and psycho-acoustics.Building on a tradition of excellence and innovation in acoustic testfacilities, Eckel now offers an expanded range of quality-engineered anechoic chambers and hemi-anechoic chambers tomeet virtually any testing range requirements – with low frequencycutoffs down to 40 Hz . . . and any testing space needs – from thelargest, custom-engineered, double-walled acoustic structures to

the smallest portable anechoic chambers.Eckel’s modular attenuating structures have guaranteed perform-ance and incorporate numerous state-of-the-art features, including• the NEW EMW PERFORATED METALLIC ANECHOIC WEDGEwhich combines outstanding performance, long-term acousticintegrity, and lightweight • special track system for efficient instal-lation of wedges • unique cable floor design • sound attenuatingdoors • instrumentation sleeves and supports • ventilation • lightingand power systems. Plus Eckel offers integrated design andengineering services and turnkey capability.For full details, contact

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The Peabody Institute of the Johns Hopkins University now requires students to complete a 2 credit

course, “Professional Practices in Acous-tical Consulting,” as part of the school’s graduate degree program in acoustics. The course, developed and to be taught by NCAC member Neil Thomp-son Shade, will emphasize the profes-sional, business, and inter-personal fac-tors of running an acoustical consulting practice. Topics to be covered will include cli-ent relations and motivation, marketing, legal aspects of small business structure, insurance, contracts and AIA standard

Listed below is contact information for the NCAC Board of Directors.

Past President/LRPCK. Anthony Hoover(978) [email protected]

PresidentEdward L. Logsdon, [email protected](303) 455-1900

President ElectDavid E. [email protected](800) 229-7444

Vice President/FinancesDavid A. [email protected](818) 991-9300

Professional Practices Course in Acoustical Consulting

forms of agreement, professional ethics, dispute resolution, fi nancial planning and professional fees, project phases, con-struction doc-uments, and the construc-tion process. The Pea-body acous-tics program, in existence since 2002, has graduated 10 students all of whom are employed by acoustical consulting or audio/visual design fi rms,

NCAC Board of Directors ContactsProfessional PracticesJack Randorff, [email protected](806) 829-2521

MembershipKerrie G. [email protected](503) 646-4420

Individual Member RepresentativeJames E. [email protected](510) 658-6719

DirectorRuss [email protected](972) 661-5222

Director-at-LargeBennett [email protected](860) 647-0514

Director-at-LargeBill [email protected](805) 771-8434

Director-at-LargeNeil Thompson [email protected](410) 821-5930

loudspeaker manufacturers, and acousti-cal material manufacturers, or are pursu-

ing Ph.D. degrees. [NTS].


Advertisers in this issue:

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NCAC encourages ad ver -tis ing of acoustical products, services, and sys tems in the NCAC News let ter as a means of im prov ing com mu ni ca tion with the acous ti cal con sult ing pro fes sion. Acceptance of advertising does not imply en dorse ment of products or services by the Na tion al Council of Acous ti cal Consultants or any of its individual mem bers. Newsletter read-ers are invited to contact the advertisers directly for additional product techni cal and cost information or to advise of possible mis lead ing in for ma tion in their ad ver tise ments.

EmploymentATS Consulting is looking for a person with engineering or related background who is interested in a consulting career in acoustics. ATS specializes in noise and vibration studies for surface trans-portation systems and is an international leader in rail noise and vibration control. Projects would range from fi nite element studies of vibration generated by subway systems to small acoustical studies for new residential developments. Previous experience is desirable, but not required. Technical areas coved by this position in-clude: transportation noise and vibration control, building acoustics, rail engineer-ing, related surface transportation areas (pavements, rail traffi c), sound propa-gation, atmospheric effects, numerical methods (particularly fi nite elements), applied math, and physics. Previous experience is not required, although candidates should have dem-onstrated the ability to prepare technical reports and be capable and interested in learning new technical areas. Desirable qualifi cations and interested include:• B.S. or B.A. in acoustics, mechani-cal engineering, structural engineering, or related fi eld. Advanced degrees are highly desirable.• Interests in transportation, acoustics, vibration, railroads, computer methods.• Motivated and interested in the fi eld of transportation noise and vibration.• Interested in a career with a consult-ing fi rm.

• Excellent writing and quantitative skills.• Able to communicate directly with clients.• Authorized to work in the US.• Computer savvy with substantial experience using Microsoft Excel and Work applications.• Capable of taking responsibility for small projects in relatively short time.• Excited about being part of a small and growing company.

Hugh SaurenmanATS Consulting, LLC725 S. Figueroa Street, Suite 1580Los Angeles, CA 90017Tel: 213.488.7770, Fax: 213.488.0270Email: [email protected]

For SaleNorsonic type 213 dodecahedral loud-speaker with stand $775.00; Norsonic type 250 half-dodecahedral loudspeaker $850.00; Norsonic type 260 power am-plifi er with noise source $875.00; Bogen 12 ft “boom” heavy-duty tripod $40.00; Norsonic 1220 ½ inch free fi eld micro-phone capsule (type 1, 200 V polariza-tion) $75.00; microphone windscreens for ½ inch mics $15.00 each. LEMO-LEMO mic cables 10 m quantity 2 $35.00/each. Or make offer. All excellent condition and “low mileage”. Buyer pays shipping. [email protected].

Classifi ed

“Well, I’ll be darned, maybe they are serious about restructuring.”

© 1994 Charles Barsotti