the frequency spectrum stored by the input signal and the noise estimate (113) comparing (114 115) to the voice and noise are distinguished. under the control of the auxiliary detector (200) updating a noise estimate in the voice-less period (in a buffer (113)). In order to improve the operating signal (for example signal tone) having a strong harmonic component exists according to the input (x (i)) and from the filter having a response complementary to the spectrum of the input (105) of the residual signal (y (i)) calculates the LPC prediction gain of the input filter is obtained if the gain exceeds a threshold the buffer update is prohibited.

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.

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.