Apparatus for the detection of voice signals

A detection apparatus for receiving an input signal containing noise and for detecting therein the presence of voice signals comprising:

• a threshold voltage generator having a control input and an output for supplying a threshold voltage which either rises exponentially as a function of time in accordance with a first time constant which exceeds a maximum syllable period, or drops exponentially in accordance with a second time constant which exceeds the maximum pitch period;
• control means having a first and a second input for respectively receiving the input signal and the threshold voltage and an output coupled to the control input of the generator for supplying a control signal making the threshold voltage rise as long as the input signal peak amplitude is greater than the threshold voltage, and making it drop in the opposite case;
• attenuation means in a ratio k (k being equal to a positive integer which is not zero) for receiving the input signal and having an output for supplying an attenuated signal;
• comparison means for comparing the amplitude of the attenuated signal with the threshold voltage and having an output for supplying a first intermediate signal when the amplitude of the attenuated signal exceeds the threshold voltage;
• decision means coupled to the output of the comparison means for supplying a signal corresponding to a detection of voice signal when the first intermediate signal shows a burst of transitions whose total duration is greater than T.sub.S (the lower bound of the syllabic period) and when each two successive transitions in the same direction is separated by a time interval lower than Tn (the upper bound of the pitch period).