| 摘要 |
Speech is distinguished from noise by a spectral comparison (114, 115) of an input signal with a stored noise estimate (113). Updating of the noise estimate (in a buffer (113)) is permitted during periods when speech is absent under control of an auxiliary detector (200). In order to improve operation in the presence of signals with strong harmonic components (e.g. signalling tones) an LPC prediction gain is computed from the input (x(i)) and a residual (y(i)) obtained from the input following filtering by a filter (105) having a response complementary to the frequency spectrum of the input, and if the gain exceeds a threshold, buffer updating is suppressed.
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