osha noise vibra

7/21/2019 Osha Noise Vibra

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A. Sound Level Meters

Application and Principle of Operation:

The sound level meter (SLM) is the basic instrument for investigating noise levels. t can

be used to evaluate area noise levels! to identif" noise sources! estimate emplo"eee#posures and aid in determining solutions for noise control. The SLM consists of a

microphone! a preamplifier! an amplifier $ith an ad%ustable and calibrated gain!

fre&uenc" $eighting filters! meter response circuits! and an analog meter or digitalreadout. A'S has classified levels of precision for sound level meters as T"pe

(laborator" standard)! T"pe (precision measurements in the field)! and T"pe (general

purpose measurements). The T"pe meter is most fre&uentl" used in the field for

emplo"ee e#posure and noise evaluation purposes.

Most SLMs allo$ options for linear! A! and fre&uenc" $eighting. n addition! either

*slo$* or *fast* meter response can be selected. +ith fast response! the meter closel"

follo$s the sound level as it changes. A slo$ response is more sluggish but allo$s theuser to obtain a better average of the changing sound level. The OS,A noise standards

re&uire e#posure measurements to be made $ith a slo$ meter response on the A scale.

Some SLMs have an *impulse* or *pea-* response for monitoring impulsive sounds. The

pea- value is the ma#imum value of the $aveform! $hile the impulse response is anintegrated measurement. Onl" the pea- value should be used $hen measuring pea- levels

for compliance $ith the OS,A / decibel (d0) pea- sound pressure level.

0. 'oise 1osimeters


A noise dosimeter is essentiall" an SLM that integrates noise levels over the sampling

period and calculates the noise dose. t is the primar" instrument used for compliance

measurements. The noise dosimeter is $orn b" an individual during sampling to calculatepersonal noise dose! or it can be placed in a specific location to measure the sound level

in that area.

Specific instrument settings can be selected on a noise dosimeter! including e#changerate! fre&uenc" $eighting! fast or slo$ response! criterion level! and threshold. 2efer to

Section ! hapter 3for additional information.

. Octave 0and Anal"4ers


An octave band anal"4er is a t"pe of SLM $hich can separate the monitored noise into

specific fre&uenc" bands! $hich is necessar" $hen anal"4ing noise sources to develop

noise control solutions. This information is also useful in selecting hearing protectors b"
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calculating the amount of attenuation for specific fre&uenc" bands. Most octave band

anal"4ers filter the sampled noise spectrum into 5 or octave bands! $hile some

anal"4ers can measure noise in one6third octave bands for an even more detailed anal"sis.7suall"! a T"pe (precision) SLM is used for octave band anal"sis.

1. Sound ntensit" Anal"4ers


Ordinar" SLMs measure sound pressure level! $hich indicates the level of the sound! but

not the direction from $hich the sound is coming. A sound intensit" anal"4er can

measure intensit"! $hich is a measure of both the magnitude and direction of the sound

energ". +ith an intensit" anal"4er! noise sources can be specificall" identified and ran-edaccording to sound po$er. This anal"sis can often be performed in environments $here

the noise is reverberant! since the intensit" anal"4er indicates the direction of the noise. A

sound intensit" anal"4er is particularl" useful for pinpointing noise sources and

determining appropriate engineering controls.

alibration:

'oise instruments are usuall" calibrated at the field site before and after each use!

according to the manufacturer8s instructions. alibration is accomplished b" using anacoustic calibrator $hich applies a -no$n sound pressure level to the microphone! and

the instrument is ad%usted to read the proper level. n addition to user calibration! some

instruments ma" re&uire routine factor" calibration and maintenance! such as ever" 69

"ears.

Special onsiderations:

Some general considerations for using noise monitoring e&uipment are listed belo$. ach

t"pe of e&uipment should be used according to the manufacturer;s instructions.

Additional factors to consider are included in Section ! hapter 3.a. 0atteries should al$a"s be chec-ed prior to use.

b. 0e careful $ith microphone cables. 'ever -in-! stretch! pinch or other$ise damage the

cables.

c. 7se a microphone $indscreen $hen e&uipment is used outdoors or in dust" or dirt"areas.

d. 'ever use an" t"pe of covering on the microphone (e.g.! plastic bag or plastic $rap) to

protect it from moisture. These materials $ill distort the noise entering the microphone!and the readings $ill be invalid.

e. 'ever tr" to clean a microphone! particularl" $ith compressed air! since damage is

li-el" to result.f. 2emove the batteries from an" meter that $ill be stored for more than a fe$ da"s.

Protect meters from e#treme heat and humidit".

,2T Availabilit":
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The ,2T maintains the follo$ing speciali4ed noise anal"sis e&uipment $hich can be

used for noise e#posure and engineering control evaluations:

a. 0ruel < =%aer 99> Anal"4er

The 0 is a multipurpose T"pe sound level meter and octave band anal"4er. t

can also be operated as a sound intensit" anal"4er for identif"ing noise sources anddetermining engineering controls. n addition! the 99> includes a building acoustics

s"stem for measuring noise deca" and determining the reverberation characteristics for a

given room. 0ased on the noise deca" data! calculations can be performed to estimatepotential noise reduction if absorptive materials are applied to room surfaces! such as the

$alls and ceiling.

b. Larson 1avis Spar-? @3 1osimeters

The Larson 1avis Spar- @3 1osimeter is a super6dut" dosimeter contained in a sealed!

$aterproof! intrinsicall" safe metal housing. The dosimeters have no controls or displa"s!

$hich eliminates the possibilit" of tampering or damage b" the individual $earing themonitor. The dosimeters are programmed and controlled b" use of a remote control unit

or personal computer. The remote control unit (model @>2) can also be operated as anadditional dosimeter. 1ata is transferred from the @3 via an infrared port on the

dosimeter housing. ibration Monitors

The follo$ing sections contain a brief discussion of various t"pes of measurements that

are of concern $hen measuring vibration. ,uman response to vibration is dependant on

several factors! including the fre&uenc"! amplitude! direction! point of application! time ofe#posure! clothing and e&uipment! bod" si4e! bod" posture! bod" tension! and

composition. A complete assessment of e#posure to vibration re&uires the measurement

of acceleration in $ell6defined directions! fre&uencies and duration of e#posure. Thevibration $ill generall" be measured along B (#! " and 4) a#es.

A t"pical vibration measurement s"stem includes a device (accelerometer) to sense thevibration! a recorder! a fre&uenc" anal"4er! a fre&uenc"6$eighting net$or-! and a displa"

such as a meter! printer or recorder. The accelerometer produces an electrical signal in

response to the vibration. The si4e of this signal is proportional to the acceleration applied

to it. The fre&uenc" anal"4er determines the distribution of acceleration in differentfre&uenc" bands. The fre&uenc"6$eighting net$or- mimics the human sensitivit" to

vibration at different fre&uencies. The use of $eighting net$or-s gives a single number

as a measure of vibration e#posure (i.e.! units of vibration) and is e#pressed in meters persecond s&uared (mCs9).

A. ,and6arm ibration


,and6arm vibration $ill generall" be measured $hen using a hand6held po$er tool. Dirst!


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one must determine the t"pe of vibration that $ill be encountered since a different

accelerometer $ill be used depending on $hether an impact (e.g.! %ac- hammer or

chipper) or non6impact (e.g.! chain sa$s or grinders) tool is being used. Theaccelerometer $ill be attached to the tool so the a#es are measured $hile the emplo"ee

grasps the tool handle. The 4 a#is is generall" from the $rist to the middle -nuc-le! the #

a#is is from the top of the hand do$n through the bottom of the hand and $rappedfingers! and the " a#is runs from right to left across the -nuc-les of the hand. The

measurement should be made as close as possible to the point $here the vibration enters

the hand.

The fre&uenc"6$eighting net$or- for hand6arm vibration is given in the nternational

Organi4ation for Standardi4ation (SO) standard SO 3B/5. The human hand does not

appear to be e&uall" sensitive to vibration energ" at all fre&uencies. The sensitivit"appears to be the highest around E6> ,4 (,ert4 or c"cles per second)! so the $eighting

net$or-s $ill generall" emphasi4e this range. ibration amplitudes! $hether measured as

fre&uenc"6$eighted or fre&uenc"6independent acceleration levels (mCsec9)! are generall"

used to describe vibration stress (American 'ational Standards nstitute! Americanonference of Fovernmental ndustrial ,"gienist! SO! 0S). These numbers can

generall" be read directl" from the human vibration meter used.

The recommendations of most advisor" bodies are based on an e#posure level li-el" to

cause the first signs of Stage ,and6Arm ibration S"ndrome ($hite finger) inemplo"ees.

0. +hole6bod" ibration


The measurement of $hole6bod" vibration is important $hen measuring vibration fromlarge pieces of machiner" $hich are operated in a seated! standing! or reclined posture.

ibration is measured across three (#! " and 4) a#es. The orientation of each a#is is as

follo$s: 4 is from head to toe! # is from front to bac- and " is from shoulder to shoulder.The accelerometer must be placed at the point $here the bod" comes in contact $ith the

vibrating surface! generall" on the seat or against the bac- of the operator.

The measurement device is generall" an accelerometer mounted in a hard rubber disc.This disc is placed in the seat bet$een the operator and the machiner". are should be

ta-en to ensure that the $eight of the disc does not e#ceed more than about G of the

$eight of the person being measured.

alibration:

ibration e&uipment $ill not generall" be calibrated b" the user. These devices $ill

generall" be sent bac- to the manufacturer for calibration on an annual basis.

Special onsiderations:


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OS,A does not have standards concerning vibration e#posure. The American onference

of Fovernmental ndustrial ,"gienists (AF,) has developed Threshold Limit alues(TLs) for vibration e#posure to hand6held tools. The e#posure limits are given as

fre&uenc"6$eighted acceleration. The fre&uenc" $eighting is based on a scheme

recommended in SO 3B/5. ibration6measuring instruments have a fre&uenc"6$eightingnet$or- as an option. The net$or-s list acceleration levels and e#posure durations to

$hich! AF, has determined! most emplo"ees can be e#posed repeatedl" $ithout

severe damage to fingers. AF, advises that these values be applied in con%unction$ith other protective measures! including vibration control.

The most $idel" used document on $hole6bod" vibration is the *Fuide for the

valuation of ,uman #posure to +hole 0od" ibration (SO 9>B).* These e#posureguidelines have been adopted as AF, TLs.

The SO standard suggests three different t"pes of e#posure limits for $hole bod"

vibration! of $hich onl" the third is generall" used occupationall" and is the basis for theAF, standard:

. The reduced6comfort boundar" is for the comfort of passengers in airplanes! boats! andtrains. #ceeding these e#posure limits ma-es it difficult for passengers to eat! read or

$rite $hen traveling.

9. The fatigue6decreased proficienc" boundar" is a limit for time6dependent effects that

impair performance. Dor e#ample! fatigue impairs performance in fl"ing! driving and

operating heav" vehicles.

B. The e#posure limit is used to assess the ma#imum possible e#posure allo$ed for

$hole6bod" vibration. There are t$o separate tables for e#posures. One table is for

longitudinal (head to toeH 4 a#is) e#posures! $ith the lo$est e#posure limit at / 6 E ,4based on human bod" sensitivit". The second table is for transverse (bac- to chest and

side to sideH # and " a#es) e#posures! $ith the lo$est e#posure limit at I 9 ,4 based on

human bod" sensitivit". A separate set of *severe discomfort boundaries* is given for E6hour! 96hour and B6minute e#posures to $hole6bod" vibration in the .I.>B ,4 range.

AF, recommendations are based on e#posure levels that should be safe for repeated

e#posure! $ith minimal ris- of adverse effects (including pain) to the bac- and the abilit"

to operate a land6based vehicle.

Some general considerations for using vibration e&uipment include:

a. 0atteries should al$a"s be chec-ed prior to use.b. 0e careful $ith electrode cables. 'ever -in-! stretch! pinch or other$ise damage the

cables.

c. 2emove the batteries from an" meter that $ill be stored for more than a fe$ da"s.d. Protect meters from e#treme heat and humidit".

,2T Availabilit":

The ,2T maintains the follo$ing vibration anal"sis e&uipment:


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a. Larson 1avis ,uman ibration Meter 6 ,M

The ,M is a portable multipurpose meter $hich can be used for measurement of$hole6bod" vibration! hand6arm vibration! hand6tool vibration! vibration severit" and

product compliance testing. t $ill collect and anal"4e data in accordance $ith the most

current SO re&uirements for hand6arm vibration and $hole6bod" vibration e#posures. tmeasures three input channels simultaneousl"! and a fourth channel calculates and stores

vector sum information. Single and tria#ial accelerometers attach to speciali4ed

mechanical mounting adaptors to allo$ measurement on a $ide variet" of tools andsurfaces.

. Mechanical Dorce Fauge for rgonomic valuations


Mechanical force gauges are fre&uentl" used for a $ide range of force testing

applications including testing of compressive andCor tensile forces. The gauges ma" be

mounted to a test stand for even greater control and consistent results in repetitive testingapplications. An eas" to read concentric dial measures cloc-$ise direction onl". The dial

rotates B>6degrees for tarring. A pea- hold button captures pea- readings. 7suall" thegauges are available in lbf! -gf or ' units of measure.

alibration:

Fauge accurac" should be chec-ed periodicall" to ensure the gauge is $ithin its

calibration limits. The calibration can be verified b" appl"ing -no$n $eight (ad%usted for

local gravit") to the e#tension hoo-. f ad%ustment is re&uired! the gauge should bereturned to the manufacturer for calibration.

osha noise vibra

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