Abstract: A process and apparatus (a) for reducing the perceived noise without perceptible loss of fidelity upon aural reproduction, of an audio input signal in electrical form by means of an electronic circuit wherein the upper limit of the bandwidth of the signal is automatically and continuously adjusted in accordance with the relationship of (i) the peak amplitude of the rate of change of the signal with respect to time to (ii) the instantaneous amplitude within a selected frequency band of the signal, and (b) a system for detecting and discriminating between noise and audio transients in the input signal and retaining the audio transients in the output signal.