4,223,180

43.70.Gr HUMAN SPEECH ENVELOPE TRACKER

Thomas L. Eckels, assignor to the United States of America 16 September 1980 {Class 179/1 SC); filed 22 December 1978

Speech waveform envelope tracking is often based on an averaging technique such as rms averaging or charge/discharge time functions such as used in agc circuitry. An envelope peak follower is disclosed here which rectifies the waveform, then latches the peak value at the point where the first derivative is zero. The amplitude of each peak is taken as the envelope value until another peak is detected.--DLR

4,219,695

43.70.Lw NOISE ESTIMATION SYSTEM FOR USE IN

SPEECH ANALYSIS

Arthur L. Wilkes, Fred B. Wade, and Robert L. Thompson, assignors to International Communication Sciences

26 August 1980 (Class 179/1 P}; filed $ October 1977

This patent covers an adaptive voiced/unvoiced decision method based on the relative energy in the first autocorrelation coefficient. In order to illustrate the application of the V/UV decision logic, the entire pitch- excited, linear prediction vocoder is described. The vocoder uses a eepstrum pitch tracker and an autocorrelation LPC analysis. The autocorrelation is computed from a truncated version of the window used for the cepstrum. In the V/UV threshold adaptation, the threshold level is filtered such that it tends to seek the lowest excursions of the first autocorrelation coefficient as

a means of normalization to the signal amplitude.--DLR

4,223,182

43.70.Lw TRANSMISSION OF SIGNALS WITH

PRIVACY

John M. Fraser, assignor to Bell Telephone Laboratories 16 September 1980 (Class 179/1.5 R); filed 27 September 1944

This patent was originally applied for during World War II and was just recently issued. The patent discloses the concept of a two-stage speech encryption device, where each of the stages performs scrambling essentially independent of the other stage. The only common link is that a single se- quence generator determines the patterns in both stages. The example given consists of a time scrambler for the first stage and a frequency band scram- bler for the second stage, each individually disclosed in prior patents. All the circuitry details are given in terms of relays and multiple-head tape loops, although this now quaint implementation is not reflected in the claims.-- DLR

4,227,046

43.70.Sc PREPROCESSING SYSTEM FOR SPEECH RECOGNITION

Akira Nakajima and Aldra Ichikawa, assignors to Hitachi, Limited 7 October 1980 (Class 179/1 SD); filed in Japan 25 February 1977

A spectral corrector is described which filters an incoming speech sig- nal, modifying the signal so as to give it a predetermined average spectral shape. The target spectrum may be obtained by connecting a "standard" signal which contains no transmission line characteristic effects. The filter- ing is done by a pair of PARCOR lattice filters, the first having corrclators in the circuit at the coefficient input points of each stage. The outputs of the correlators may be stored and fed into the second lattice filter as the PAR- COR coefficients for that filter.--DLR

4,220,819

43.70.Lw RESIDUAL EXCITED PREDICTIVE SPEECH CODING SYSTEM

Bishnu S. Atal, assignor to Bell Telephone Laboratories 2 September 1980 {Class 179/1 SA); filed 30 March 1979

A residual-excited, linear prediction vocoder is disclosed which trans- mits information on the spectrum of the residual in the form of ten spectral energy coefficients extracted by a filter bank. LPC reflection coefficients are computed by the covariance method, and the pitch is tracked by a cepstral peak analysis. A voiced/unvoiced decision is based on the residual energy, the first prediction coefficient, the first autocorrelation coefficient, and a zero-crossing count. Transmitted parameters include LPC coefficients, pitch, V/UV decision, and the ten residual spectrum values. In the receiver, a traditional pulse/noise excitation formed from the pitch information is fed into a bank of ten filters corresponding to the residual analysis bank. In both transmitter and receiver, the filters consist of the squared sums of 27-point FIR cosine/sine pairs at the respective center frequencies. The filter band outputs, gain controlled by the received parameters, are summed to form the excitation for the LPC synthesizer.--DLR

4,450,749

43.75.Mn METHOD AND APPARATUS FOR RECORDING AND REPRODUCING PEDALING

EFFECTS IN A PIANO PERFORMANCE

Wayne L. Stahnke, Los Angeles, CA 29 May 1984 (Class 84/462); filed 23 April 1982

Player pianos seldom provide adequately controlled operation of the sustain and soft pedals used to operate the piano damper mechanism. This

4,221,931

43.70. Lw TIME DIVISION MULTIPLIED SPEECH SCRAMBLER

Norman C. Seiler, assignor to Harris Corporation 9 September 1980 {Class 179/1.5 R); filed 17 October 1977

A speech encryption system is disclosed which uses three forms of randomization. First, the speech signal is filtered into high- and low-fre- quency bands which are randomized independently. Second, within each band, randomly selected intervals of the signal are time reversed prior to further encryption. Third, within each interval, the signal values are time scrambled according to a 68-stage shift register pseudonoise sequence gen- erator.--DLR

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1602 J. Acoust. Soc. Am. 76(5), Nov. 1984; 0001-4966/84/111602-02500.80; ¸ 1984 Acoust. Soc. Am.; Patent Reviews 1602

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