| 摘要 |
In a digital speech detector, a first detector (601) produces an output signal if any sample of a voice channel signal has a magnitude (T) exceeding a fixed threshold (TF) above noise levels. A second detector (602) produces a second threshold (TL) which is adaptively adjusted to noise levels on the channel by being set to a level above the current sample magnitude (T) each time that this does not exceed the preceding sample's magnitude (TP). When the sample magnitude (T) rises above the second threshold (TL), and for each subsequent sample of successively increasing magnitude, the second detector (602) produces an output signal. A speech decision for the voice channel is reached if either detector (601, 602) produces its output signal. The output signals of the first and second detectors (601,602) are maintained for fixed and variable, respectively, hangover periods to maintain the speech decision during intersyllabic pauses in speech. The samples are supplied to the speech detector by an offset remover and averaging circuit.
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