5,263,089

43.66.Ts HEARING AID

Zlatan Ribic, assignor to Viennatone GmbH 16 November 1993 (Class 381/68.2); filed in Austria 7 November

1990

This patent relates to a hearing aid circuit with a filter of higher order for controlling the frequency response. The filter can be placed between two stages or in a feedback loop of the amplifier. To obtain optimal adjustment of the frequency response, the filter is arranged as a multiple filter with a biquadratic structure and has at least two integrators and an inverting amplifier. An adjustable potentiometer is provided for setting responses. There is another potentiometer in the filter circuit for setting the mid-frequency of the filter. BSFL

5,263,090

43.66.Ts HEARING AID FILTER APPARATUS

Richard A. Hughes, Greencastle, Pennsylvania 16 November 1993 (Class 381/69); filed 31 January 1992

The patent shows a sock arrangement that fits over a behind-the-ear hearing aid to protect it from dust or similar contamination. In addition to the sock, a series of hair filaments mounted above it support the wear- er's hair above the sock and given additional protection against contamination.BSFL

5,195,137

43.72.Ar METHOD OF AND APPARATUS FOR

GENERATING AUXILIARY INFORMATION FOR EXPEDITING SPARSE CODEBOOK SEARCH

Kumar Swaminathan, assignor to AT&T Bell Laboratories 16 March 1993 (Class 381/32); filed 28 January 1991

Here is another method of speeding up the codebook search in a CELP vocoder. In this case, auxiliary information used for computing the distortion metric and the energy level is precomputed for each nonzero codebook entry. Nonzero entries are located using a stored offset, further speeding up the search.•DLR

5,195,138

43.72.Ar VOICE SIGNAL PROCESSING DEVICE

Joji Kane and Akira Nohara, assignors to Matsushita Electric Industrial Company

16 March 1993 (Class 381/46); filed in Japan 18 January 1990

This sPeech signal detector computes a cepstrum and its mean value from frames of the input signal. The cepstral peak is located and its frequency used to determine an analysis interval. The peak value is corn-

5,214,708

43.72.Ar SPEECH INFORMATION EXTRACTOR

Robert H. McEachern, Edgewater, MD 25 May 1993 (Class 381/48); filed 16 December 1991

This novel technique for extracting speech parameters uses ratio detectors to process the band outputs of a log-spaced Gaussian-response filter bank. The result is AM and FM detection of each harmonic of the

fundamental across a low-frequency portion of the speech signal. This allows determination of the spectral envelope exceeding the time-

Speech Waveform

....... .,.........._..'_ ..•-• .;._...•_.....,.... .....

;.";.-_ ;o;'.•':.::•.•'".•::;.:...'.::.'.7..•'.';? ;_:; :":

'.•.• ';...'•' :::•'•'. :..'.•_•.¾ . •.-'.k•': 3:20 Hz

CompOsite FM(t) TM

bandwidth product limitation of transform analysis and accurate recon- struction of the pitch profile. The method is said to be robust with noisy or variable speech input, and to have some speaker independent properties.--DLR

5,216,702

43.72.Dv NONINTRUSIVE SPEECH LEVEL AND

DYNAMIC NOISE MEASUREMENTS

David B. Ramsden, assignor to AT&T Bell Laboratories I June 1993 (Class 379/24); filed 27 February 1992

The patented device is a telephone circuit monitor designed to pro- vide unobtrusive measurements of the line's speech transmission quality as represented by the signal-to-noise ratio (SNR). The measurement ac- curacy is improved by detecting the short-term average power to deter- mine whether speech is present at a given moment. Either a speech or noise average power figure is updated accordingly, allowing continuous computation of the line SNR.--DLR

•ueFrenc¾

pared to a threshold based on the cepstral mean value to indicate whether the analyzed interval contains a speech signal.--DLR

5,187,745

43.72.Gy EFFICIENT CODEBOOK SEARCH FOR CELP VOCODERS

William C. Yip and David L. Barron, assignors to Motorola, Incorporated

16 February 1993 (Class 381/36); filed 27 June 1991

Code excited linear predictive (CELP) vocoders typically involve a heavy computational load in performing the codebook search. In this example, an arrangement of bit flags is scanned as the excitation vectors are tested, allowing unpopulated slots in the sparse code space to be quickly skipped over. It is not clear to this reviewer whether there is any speedup in the convolution step required to test an excitation vector.• DLR

2794 J. Acoust. Soc. Am., Vol. 95, No. 5, Pt. 1, May 1994 Review of Acoustical Patents 2794

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