ly encoded according to pulse-code modulation techniques (PCM) .... The digital codes are optically applied to the film sound track and are played back by optical detection as the film runs through a projector. The advan- tages of PCM signal-to-noise improvement are obtained, and means for the individual sample codes to be 'scrambled' on recording and 'unscrambled'

on replay are shown. The scrambling greatly increases the difficulty of sur- reptitious copying by 'film pirates.' One embodiment shown applies and detects the individual code bits through individual optical fibers and the other applies and detects codes serially using a modulated laser source and a controllable refraction optical crystal or a Bragg Cell to scan across the sound track to emplace (and replay) individual sample codes."--DWM

3,970,787

43.88.Si AUDITORIUM SIMULATOR AND THE LIKE EMPLOYING DIFFERENT PINNA FILTERS FOR HEADPHONE LISTENING

Campbell L. Searle, assignor to Massachusetts Institute of Technolo-

20 July 1976 (Class 179/1 AT); filed 11 February 1974 This is a signal processing system composed of delays, attenuation

elements, and filters. The object is to produce cues that emphasize and localize the direction of signals in respective simulated sound paths to each ear.--MDB

4,457,396

43.88.Si SOUND DEFLECTOR FOR HEADSET EARPHONES

David L. James, Tucson, AZ 3 July 1984 (Class 181/136); filed 24 September 1982

An accessory device to be placed between an earphone and the ear is shown. It has a conical deflector that directs the sound to areas in the concha and pinna other than the ear canal entrance. It is stated that better

34

hearing and less possibility of hearing damage are achieved by having the sound strike the folds of skin in the pinna before it enters the ear canal.-- SFL

4,463,223

43.88.Si HEADPHONE

Masaru Yamanoi and Hiroshi Satoh, assignors to Nippon Columbia Kabushikaisha

31 July 1984 (Class 179/156 R); filed in Japan 10 July 1981

A foldable support for two earphones has L-shaped extensions that are attached to an adjustable headband by ball and socket joints.--SFL

4,394,535

43.88.Vk SPLIT PHASE STEREOPHONIC SOUND SYNTHESIZER

Joseph P. Bingham and John F. Benford, assignors to RCA Corpora- tion

19 July 1983 (Class 179/1 GP); filed 9 March 1981

One general type of stereo synthesizer introduces suitable signal modi- fication to feed one channel, and then derives the difference between that signal and the input to feed the other channel. But suppose the monosignal to be processed comes from a television set. If it is to be fed to a separate stereo installation an audio transformer will be required for isolation. If the

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transformer has a split secondary winding, the resulting push-pull audio signals can be used to feed synthesizer circuitry and eliminate the need for a differential amplifier. The idea is clever, but the real saving would seem to lie in the second audio transformer that would otherwise be required.-- GLA

4,456,797

43.88.Vk SUBMERSIBLE PERSONAL STEREO SYSTEM

Eric E. Olsen, Milwaukee, WI 26 June 1984 (Class 179/156 R); filed 18 November 1982

A waterproof pouch to house a personal stereo cassette type player or radio is connected by a cable to a pair ofwaterproofearphones. The pouch is attached to a belt. The earphones are held by a flexible band around the head. The earphones have a rubber tip with a flexible skirt,that fits into the ear canal, and which is stated to provide a waterproof seal.--SFL

4,458,343

43.88.Zp HIGH DYNAMIC COMPLIANCE HYDROPHONE WITH HYDROSTATIC PRESSURE BALANCING

Stephen W. Tehon and Evelyn H. Monsay, assignors to the United States of America

3 July 1984 (Class 367/149); filed 7 December 1981

Like Patent 4,450,541 (reviewed below), this patent covers a modifica- tion of the hydrophone described by Tietjen in J. Acoust. Soc. Am. 69, 993 (1981). The casing 11 contains two chambers 14 and 16, both filled with oil. Hydrostatic pressure on the diaphragm 13 is balanced because it is transmit- ted into chamber 14 through the membrane 15 and the capillary tube 17.

785 J. Acaust. Sac. Am. 77(2), Feb. 1985; 0001-4966/85/020785-02500.80; ¸ 1985 Acaust. Sac. Am.; Patent Reviews 785

Redistribution subject to ASA license or copyright; see http://acousticalsociety.org/content/terms. Download to IP: 134.129.164.186 On: Sun, 21 Dec 2014 04:55:03

18 13

21

Acoustic pressure is prevented' from reaching the back of the diaphragm by the thick wall 12 and the capillary tube. The system described in this patent is to include a bellows 22 to provide compliance, which greatly increases the motion of the diaphragm. The bellows is resonant at a frequency above the operating range of the hydrophone, which extends from 100 to 1000 Hz.-- LB

4,450,541

43.88.Zp BIAS COMPENSATED OPTICAL GRATING HYDROPHONE

Byron W. Tietjen, assignor to General Electric Company 22 May 1984 (Clnss 367/149); filed 31 December 1981

Like Patent 4,458,343 (reviewed above), this patent covers a modifica- tion of the hydrophone described by Tietjen in J. Acoust. Soc. Am. 69, 993

(1981). The modified hydrophone contains two optical gratings 64 and 66, which have alternate opaque and transparent stripes in the order of 0.001 to 0.004 in. wide. One grating is attached to the moving diaphragm while the other is stationary, and their relative motion modulates light that passes

42

72a V '-,,• ... -

between the optical fibers 42 and 48, and between 44 and 50. The gratings are alike, except that one stripe 72A has only half the normal width. Conse- quently, the modulation of one light beam is 90 ø out of phase with the other. For proper operation, the hydrophone should use the phase of the modula- tion that included the bias point, i.e., the condition when the diaphragm is at rest. This is something that cannot be controlled in the manufacture. The patent describes an electronic circuit which finds the proper quadrant, se- lects which of two beams should be used to include the bias point, and if necessary reverses the phase of the output signal to bring it into phase with the displacement of the diaphragm.--LB

786 J. Acaust, Sac. Am. 77(2), Feb. 1985; 0001-4966/85/020786-01500.80; ¸ 1985 Acaust. Sac. Am.; Patent Reviews 786

Redistribution subject to ASA license or copyright; see http://acousticalsociety.org/content/terms. Download to IP: 134.129.164.186 On: Sun, 21 Dec 2014 04:55:03