System and method for modifying speech signals

Abstract

A system and method for speech signal enhancement upsamples a narrowband speech signal at a receiver to generate a wideband speech signal. The lower frequency range of the wideband speech signal is reproduced using the received narrowband speech signal. The received narrowband speech signal is analyzed to determine its formants and pitch information. The upper frequency range of the wideband speech signal is synthesized using information derived from the received narrowband speech signal.

Description

Background of the invention [0001] The present invention relates to techniques for transmitting speech information in communication networks, and more particularly to techniques for enhancing narrowband speech signals at a receiver. [0002] In the transmission of speech signals, there is a trade-off between network capacity (ie, the number of calls being transmitted) and the quality of the speech signals for those calls. Most telephone systems in use today encode and transmit speech signals in a narrow frequency band between approximately 300 Hz and 3.4 kHz according to Nyquist's theorem at a sampling rate of 8 kHz. Since human speech contains frequencies between approximately 50Hz and 13kHz, sampling human speech at an 8kHz rate and transmitting a narrow frequency range of approximately 300Hz to 3.4kHz must ignore information in the speech signal. Therefore, the telephone system necessarily degrades the quality of the speech signal. [0003] Various methods of extending th...

AI Technical Summary

Problems solved by technology

One disadvantage associated with telegraph codebooks is that they require significant training

These methods are simple and effective, but they often introduce high-frequency distortion that makes the voice metallic

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