Abstract: A voice transcoder for use in compensating for sound distortions in helium speech, including a plurality of audio frequency channels, each defining a particular frequency band, the center frequencies of the channels being logarithmically spaced and frequency bands together covering the helium speech frequency band to be transcoded. Each channel comprises a band-pass filter coupled to a detector, a divider dividing band-pass filter by detector output to provide a signal having the frequency delivered from the band-pass filter at a standard amplitude, and a mutliplier multiplying divider output by another channel detector output to synthesize a part of the transcoded audio signal, the different parts of the transcoded signal being combined in an adder-subtracter. The said multiplier has one input coupled from divider output in the channel of rank i and the other input coupled from rectifier output in the channel of rank i + x, x being the same for any multiplier.

Abstract: A detection circuit for the significant peaks of a speech signal, comprising first and second detectors respectively for detecting the positive and negative peaks of said speech signal. Each of these detectors is followed by a peak charging circuit comprising a first integrator having a relatively large discharge time constant and a comparator comparing the detected speech signal and the output signal of said first integrator. Each peak charging circuit comprises in addition a second integrator having a relatively small time-constant. The discharge of the first integrator is effected up to a voltage equal to the output voltage of the second integrator, and the discharge of the second integrator is effected down to a voltage depending on the output voltage of the first integrator. The two integrators of each peak charging circuit provide a non-exponential decreasing signal which has an inflection point following a significant peak in the original speech signal.