ARRANGEMENT FOR REDUCING THE NOISE IN A SPEECH SIGNAL MIXED WITH NOISE

In order to reduce the noise signal of an acoustic origin contained in an input signal coming from a microphone located in a noisy environment, a noise reducing arrangement includes a filter (6) which receives the input signal and eliminates a frequency band of some hundreds of Hertz, centered around the average frequency of the first formant of the speech signal, a detector circuit (7) detecting the output signal of the filter (6) with a time constant to the order of some tenths of a second, finally a variable-threshold circuit (9) which uses the detected signal as the threshold signal and which is arranged for transmitting the variations of the input signal when the latter has an absolute value which is higher than the threshold signal.