02

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SPEECH R•TE CURVE

local time base upon which the parameter targets are located. A choice of interpolation curves may also be specified for each phoneme, by which the final parameter trajectories are computed.--DLR

4,959,866

43.72.Ja SPEECH SYNTHESIZER USING SHIFT REGISTER SEQUENCE GENERATOR

Noriko Matsuo and Yukio Mitome, assignors to NEC Corporation 25 September 1990 (Class 381/51); filed in Japan 29 December 1987

This patent describes a speech synthesizer ostensibly involving a novel application of a shift register pseudorandom noise generator in a purported simplification of the synthesizer design. At least one each of voicing and voiceless excitation waveforms are stored having durations at least equal to the longest fundamental period. The shift register noise generator is long enough to form an address pointer for indexing the excitation waveforms. This allows samples of the excitation to be played out in a random sequence. There is also a comparator register that can be set up to cause a reset or other action when a particular word appears in the noise sequence.--DLR

4,979,214

43.72.Kb METHOD AND APPARATUS FOR IDENTIFYING SPEECH IN TELEPHONE SIGNALS

Chris A. Hamilton, assignor to Dialogic Corporation 18 December 1990 (Class 381/46); filed 15 May 1989

This method for detecting speech in an audio signal is based on average amplitude measurements in each of a number of frequency bins. The Four- ier transform is specified as the preferred filtering method. The system indi- cates the presence of speech if the rate of change of amplitude between sequential frames summed across all of the frequency bins exceeds a certain threshold level.•DLR

4,914,692

43.72.Ne AUTOMATIC SPEECH RECOGNITION

USING ECHO CANCELLATION

Walter T. Hartwell eta!., assignors to AT&T Bell Laboratories 3 April 1990 (Class 379/410}; filed 29 December 1987

This telephone echo canceler is intended for use in a system that calls the user and speaks an initial voice prompt, and then routes the received speech signal to a recognition system. During the first portion of the outgo- ing prompt, the system determines the characteristics of echo disturbances on the telephone line. During that period of known speech output, the sys- tem is able to adapt to the line characteristics and reduce or eliminate degra- dation of the user's first utterance caused by line echos from the final por- tion of the outgoing prompt. DSP32 source code is provided for the echo adaptor.--DLR

5,052,261

43.75.Fg COMPENSATING VALVE SYSTEM FOR BRASS INSTRUMENTS

Martin Lessen, Rochester, NY 1 October 1991 (Class 84/389); originally filed 23 November 1983

This valve system for a brass wind instrument adds to the usual three valves (that lower the fundamental frequency by a semitone, a whole tone,

4,959,865

43.72. Kb A METHOD FOR INDICATING THE

PRESENCE OF SPEECH IN AN AUDIO SIGNAL

Yoram Stettiner eta!., assignors to The DSP Group, Incorporated 25 September 1990 (Class 381/46); filed in Israel 21 December 1987

Many different schemes have been proposed for detecting the presence of speech in an audio signal. This one uses center-clipped autocorrelation as a way to measure the harmonic content in a band from 0 to about 1 kHz. A decision sequence makes a final decision based on concurrent pitch and voicing estimates as well as the harmonic measure for past and future frames.--DLR

IOl IO2 --_ •104

105 io?T io.•T III, N I

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and one and one-half tones, respectively) a fourth valve which lowers the tone frequency by two tones. It is said that this provides a chromatic scale with more accurate intonation.•DWM

1791 J. Acoust. Soc. Am., Vol. 91, No. 3, March 1992 Patent Reviews 1791

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