SPEECH SIGNAL TRANSMISSION WITH ENHANCED BACKGROUND NOISE SOUND QUALITY

A speech transmission method which is applied to a speech coding and decoding system performing VOX (Voice Operated Transmitter) processing. The method can reduce an unfamiliar feeling of background noise to be outputted on the reception side. The method includes the steps of generating a background noise updating signal when a pause period is detected, and calculating a quantized spectrum, a non-quantized spectrum envelope and a quantized spectrum envelope from an input speech signal in the pause period on the transmission side. When a difference between the non-quantized spectrum envelope and the quantized spectrum envelope is larger than a predetermined threshold value, the quantized spectrum is changed and the background noise updating signal is produced based on the changed quantized spectrum.