Patent ID: 8600078

Claim:
An audio signal amplitude adjusting device for adjusting the amplitude of an input audio signal, comprising: a variable attenuator that increases or attenuates the amplitude of said input audio signal according to a gain signal, thereby obtaining an amplitude-adjusted audio signal; and a gain control part that generates said gain signal constituted by a series of gain values, based on a result of comparison between a level of said amplitude-adjusted audio signal and a predetermined reference level, wherein said gain control part comprises: a regular recovery part that, if the sequence of the gain values indicated by said gain signal is not in a decreasing trend or is in the decreasing trend but a decreasing degree is lower than a predetermined gain reduction level, and an envelope level of said amplitude-adjusted audio signal is lower than said predetermined reference level and higher than a predetermined minute audio level, changes the sequence of the gain values of said gain signal to a sequence of gain values where the gain value increases each predetermined first period, as said gain signal; a minute audio recovery part that, if the sequence of the gain values indicated by said gain signal is not in the decreasing trend or is in the decreasing trend but the decreasing degree is lower than the predetermined gain reduction level, and said envelope level is lower than said minute audio level and higher than a predetermined noise level, changes the sequence of the gain values of said gain signal to a sequence of gain values where the gain value increases each second period, as said gain signal, the second period being shorter than said first period; a gain reduction recovery part that, if the sequence of the gain values indicated by said gain signal is in the decreasing trend and the decreasing degree is higher than the predetermined gain reduction level, and a shift from a state where said envelope level is higher than said reference level to a state where said envelope level is lower than said reference level has occurred, changes the sequence of the gain values of said gain signal to a sequence of gain values where the gain value increases each third period, as said gain signal, the third period being shorter than said first period; and a noise gate part that, if the sequence of the gain values indicated by said gain signal is not in the decreasing trend or is in the decreasing trend but the decreasing degree is lower than the predetermined gain reduction level, and said envelope level is lower than said noise level, changes the sequence of the gain values of said gain signal to a sequence of gain values where the gain value is constant, as said gain signal.