5,317,643

43.38.Si AUDIO HELMET APPARATUS

Richard D. Patricelli, Aberdeen, WA 31 May 1994 (Class 381/187); filed 8 February 1993

Details of mounting and retaining earphones and a radio receiver in a welder's helmet are described. While entertainment of the wearer during his work is anticipated, one might question the advisability of such a system from a safety standpoint.--MDB

5,323,458

43.38.Si ECHO CANCELLATION IN A FULL-

DUPLEX SPEAKERPHONE

Sangil Park and Garth D. Hillman, assignors to Motorola Incorporated

21 June 1994 (Class 379/390); filed 25 October 1993

In one version of the system, "a direct-path echo cancellation circuit includes a loudspeaker 12, first and second microphones 14, 16, and an in-phase signal cancellation circuit 21. The first and second microphones are positioned adjacent the loudspeaker in order to receive in-phase direct-path

I t I SPEAKERPHONœ ! • 28 T• I ! I s•,• I I,,,,L

,__.•7•. ..... •'1 ,

echo components 31, 32 of the output signal from the loudspeaker...Direct- path echo cancellation helps to reduce howling and/or oscillation in a full- duplex speakerphone system. Also, direct-path echo cancellation provides more dynamic range."--MDB

5,327,506

43.38.Si VOICE TRANSMISSION SYSTEM AND METHOD FOR HIGH AMBIENT NOISE CONDITIONS

George M. Stites III, Linwood, NJ 5 July 1994 (Class 381/169); filed 3 May 1993

A control circuit for a voice transmission system includes an earpiece that may be inserted into the ear canal of a user. The earpiece is fitted with tubes that transmit outbound sound generated in the occluded ear canal to a microphone and feeds inbound sounds from an earphone. The control circuit incorporates switching for alternately activating the outbound and inbound audio circuits.---MDB

5,379,450

43.38.Si RADIO LOUDSPEAKER TELEPHONE DEVICE CAPABLE OF AUTOMATICALLY

PREVENTING HOWLING ON EXECUTION OF

CALLING OPERATION

Naoki Hirasawa and Yukio Murata, assignors to NEC Corporation

3 January 1995 (Class 455/54.2); filed Japan 28 October 1991

Interlinked detector circuits and timers prevent an unterminated loop that otherwise produces acoustic feedback between loudspeaker and micro-

phone. The patent document is easy to follow and includes considerable background information about radio speakerphones.--GLA

5,400,399

43.38.Si SPEECH COMMUNICATION APPARATUS

EQUIPPED WITH ECHO CANCELLER

Yuji Umemoto et al., assignors to Kabushiki Kaisha Toshiba 21 March 1995 (Class 379/388); filed in Japan 30 April 1991

This patent pertains to a speech communications station using a mi- crophone mounted in an acoustical space such as an office or an automobile. Upon activation of the hands-free or speaker-phone mode, earlier systems often required a certain duration of speech in order to adapt to the room characteristics. Room echoes would be heard during this interval. This sys- tem generates a brief chirping tone from the loudspeaker at the activation of hands-free mode, which allows an immediate pre-tuning of the echo canceller.--DLR

5,402,447

43.38.Si SPEECH DECODING IN A ZERO BER

ENVIRONMENT

Edward M. Roney IV, assignor to Motorola, Incorporated 28 March 1995 (Class 375/340); filed 5 March 1993

This consists of a rearrangement of the error detection and correction codes, such as used in a cellular phone, in order to conserve processing time and thus, battery power. A typical convolutional decoder performs a trans- formation on the received signal which results in a block of recovered data together with a count of the transmission bit errors. In a cellular phone, the data block includes both coded voice data and control signals. Since these two types of signals have different error tolerances, a full error recovery wastes processing time. Here, a simpler partial decoding determines whether the control signals are uncorrupted. If so, further processing can be reduced.•DLR

5,412,733

43.38.Si ACOUSTIC REPRODUCING APPARATUS

Atsushi Nagayoshi etaL, assignors to Matsushita Electric Industrial Company

2 May 1995 (Class 381/74); filed in Japan 19 January 1990

The patent relates to the use of an open-air type earphone used for listening to reproduced sound in a noisy environment. A filter is provided to attenuate sound leakage from the earphone, and another filter is provided to diminish the effect of ambient noise on the signal being heard.--SFL

5,412,736

43.38.Si PERSONAL AUDIO SYSTEM AND

EARPHONE FOR SAME

Shawn P. Keliiliki, Orem, UT 2 May 1995 (Class 381/187); filed 23 March 1992

The patent shows an earphone held in the ear by a support passing over and around the back of the ear and terminating with a connector below the earlobe. A projection on the back of the support is provided to facilitate its positioning and removal.•SFL

1833 J. Acoust. Soc. Am., Vol. 98, No. 4, October 1995 Reviews of Acoustical Patents 1833

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