At&t Bell Laboratories

American Telephone & Telegraph Co., At&t Bell Laboratories

American Telephone and Telegraph, Co.

Joseph Picone

Dimitrios P Prezas

Walter T Hartwell

Mark A Johnson

A customer inquiry unit that allows the recognition of human speech in the presence of an initial prerecorded message transmitted by the customer inquiry unit via a telephone network. The customer inquiry system is designed to be utilized to respond to inquiries received via the telephone network. The system functions by responding to a telephone call received via the network to transmit an initial speech message to the customer. Due to a variety of network problems, a portion of the speech energy of the message is reflected back to the inquiry system. This reflected energy is commonly referred to as an echo. If the customer starts to speak before the inquiry system has finished the initial message, the system utilizes an echo canceler to remove the echo received back from the telephone network and only transfers the speech response to a recognition subsystem. The echo canceler adapts to the telephone network during the initial portion of the initial speech message before the customer can respond.

Automatic speech recognition using echo cancellation

An speech analysis and synthesis system where pitch information for excitation is transmitted during voiced segments of speech and modified residual information for excitation is transmitted during unvoiced speech segments along with linear predictive coded (LPC) parameters. The speech analysis portion of the system uses a pitch detection circuit to determine when the speech is voiced or unvoiced and to calculate the pitch information during voiced segments. A multi-pulse excitation forming circuit generates the modified residual signal which is obtained from the cross correlation of the residual signal and the LPC-recreated original signal. The pitch detection circuit controls a multiplexer which selects either the output of the multi-pulse excitation forming circuit or the output of the pitch detection circuit for transmission as the excitation information with LPC parameters to the synthesizer portion of the system.

Digital speech coder with different excitation types

A pitch detector system for use with speech analysis and synthesis methods having a plurality of identical detectors each responsive to a different portion of a speech signal for estimating a pitch value and a voter circuit responsive to the estimated pitch values for determining a final pitch value. The pitch detectors are identical in design which allows for an efficient software implementation since only one set of program instructions is necessary to implement all of the encoders. The voter subsystem may be implemented by a digital signal processor executing program instructions that calculate a pitch value from the estimated pitch values determined by the pitch detectors and a second set of program instructions for constraining the final pitch value outputted by the voter subsystem so that the calculated pitch value is in agreement with calculated pitch values for previous frames. In addition, the pitch and voters may be implemented by a third set of program instructions executing on the same digital signal processor as the sets of instructions for the voter subsystem.

Growing community of inventors

Richardson, TX, United States of America

Joseph Picone