| 摘要 |
<p>SPEECH DETECTOR Samples of a transmit path voice channel signal are averaged and compared with an adaptive speech threshold to determine the presence of speech. When the average falls below a fixed threshold, a timing circuit is triggered to time a delay period followed by a noise averaging period. The timing of these periods is aborted if either the transmit path average, or a similarly produced receive path average, exceeds the fixed threshold during either period. During the averaging period the voice channel signal is averaged, and at the end of this period the average noise level is used to determine the adaptive speech threshold, a predetermined level above the average noise level, the new adaptive speech threshold being stored. The stored adaptive speech threshold is not changed unless the timing of the delay and averaging periods is completed, ensuring that only the noise is averaged to determine the adaptive speech threshold.</p> |
