REVIEW OF ACOUSTICAL PATENTS Daniel W. Martin 7349 Clough Pike, Cincinnati, Ohio 45244

The purpose of these acoustical patent reviews is to provide enough information for a Journal reader to decide whether to seek more information from the patent itself. Any opinions expressed here are those of reviewers as individuals and are not legal opinions. Printed copies of United States Patents may be ordered at $3.00 each from the Commissioner of Patents and Trademarks, Washington, DC 20231.

Reviewers for this issue:

DANIEL W. MARTIN, 7349 Clough Pike, Cincinnati, Ohio 45244 JOHN V. BOUYOUCOS, Hydroacoustics Incorporated, P.O. Box 23447, Rochester, New York 14692 SAMUEL F. LYBARGER, 101 Oakwood Road, McMurray, Pennsylvania 15317 D. LLOYD RICE, Computalker Consultants, 10126 Reseda Boulevard, # 123, Northridge, California 91324 WILLIAM THOMPSON, JR., The Pennsylvania State University, University Park, Pennsylvania 16802

5,184,332

43.30.Yj MULTIPORT UNDERWATER SOUND TRANSDUCER

John L. Butler, assignor to Image Acoustics, Incorporated 2 February 1993 (Class 367/162); filed 6 December 1990

An underwater transducer assembly comprises an electroacoustic driver unit such as a trilaminar bender 10 mounted within a housing 20 so that the opposite faces of the driver unit excite the chambers X and Y of two different size Helmholtz resonators having ports A and B that com- municate with the acoustic medium. Since the ports resonate at different

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frequencies, their acoustic outputs at frequencies between these values are additive due to two 180* phase reversals, viz., 180* because the chambers are excited by the opposite motions of the driver faces and an additional 180' because one port is excited above its resonance while the other is below. Therefore, a large dip in the transmitting response between the port resonance frequencies is eliminated. Many variations of this concept are discussed.mWT

5,052,225

43.35.Yb ACOUSTIC GYROSCOPE

Yasushi Ishii of Japan 1 October 1991 (Class 73/505); filed in Japan 20 February 1989

An acoustic gyro is defined as a device which utilizes the Coriolis force, produced when a gas vibrated by sound is subjected to rotational movement, to create a measurable effect. This is said to be an improve-

ment over prior art by forming an acoustic bridge, differentially driven by a sound source. Such an arrangement is said to eliminate calibration sensitivity to temperature and the like.--JVB

5,102,043

43.35.Ty METHOD AND APPARATUS FOR PRODUCING SNOW USING ULTRASONIC WAVES

Masanori Inoue et al., assignors to NKK Corporation 7 April 1992 {Class 239/2.2); filed in Japan 28 February 1990

Snow making machinery for ski slopes conventionally provides a mist of water which is then cooled by the surrounding air, converting the water droplets to snow. Such machinery generally requires air tempera- tures of --5 *C or lower to provide the dry snow preferred by skiers. At warmer temperatures wet snow may be produced which is less desirable. In the patent it is said that the water droplets emerging from conventional snow making apparatus are easily super-cooled by gradual heat exchange with the surrounding air; and at air temperatures close to 0*C many drops may fall to the ground before a state change occurs, even though a given droplet may have a temperature below 0 *C. Then either no snow is produced or wet snow results. The invention is said to stem from a rec- ognition that ultrasonic energy applied to the water droplets will quickly release them from the super-cooled state, thereby enabling dry snow to be produced at air temperatures close to 0 *C. The technique is said to apply equally well to the compressed air or airless apparatus for snow making.--JVB

5,038,615

43.35.Yb ULTRASONIC MULTILAYER PAINT THICKNESS MEASUREMENT

Frederick J. Trulson, August F. Scarpelli, and George L. Sarosy, assignors to General Motors Corporation

13 August 1991 {Class 73/597); filed 11 May 1990

This provides a method for automatically analyzing pulse-echo waveforms reflected from the interfaces of multilayer paint or other lam- inates, to determine the thickness of individual layers. Several ultrasonic waveforms are averaged in a digital oscilloscope and the resultant wave- form is analyzed by a computer programmed to recognize waveforms resembling pulse echoes, to compare such waveforms to stored reference waveform characteristics, and to select the waveform having the best fit to the reference. Each selected pulse echo is graded based on amplitude, peak separation, peak symmetry, and spacing from a previous echo to determine the quality of the waveform. Layer thickness is calculated from the spacing between pulse echoes and the velocity of sound in the layer material.--JVB

1179 J. Acoust. Soc. Am. 95 (2), February 1994 0001-4966/94/95(2)/1179/9/$6.00 @ 1994 Acoustical Society of America 1179

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