Method and system for reconstituting low frequencies in an audio signal

Reconstitution Procedure low frequency of an audio signal to output a playback sound (11, 12) having a low cutoff frequency (F0), comprising the steps of: - filtering the audio signal by low pass filter (101) with a cutoff frequency substantially equal to said cutoff frequency (F0) of sound reproduction device; - Determining a fundamental frequency to be reconstituted from the audio signal filtered by low baso; - Generating a harmonic signal (Sharm) associated with said fundamental frequency to be reconstituted; - Detecting a time envelope (env (t)) of the audio signal filtered by low pass; and - reinjecting said harmonic signal in said audio signal by addition after multiplication of this harmonic signal (Sharm) with the temporal envelope adapted (envadapt (t)), characterized by a dynamic adaptation stage of said temporal envelope (env (t )) depending on the frequency band considered, by compression / expansion (122a) of the temporal envelope (env (t)) with a control feedback loop (122b) of said compressing / expanding applied conditionally after comparing the level of the compressed / expanded with respect to a threshold (S) predetermined signal, and the harmonic signal phase is reinjected into said audio signal.