Patent ID: 7774201

Claim:
An acoustic apparatus, comprising: a first gain setting unit that sets a gain, A, in response to an averaged signal strength of an audio input signal within a predetermined time period; a first signal amplifying unit that adjusts a signal strength of the audio input signal based upon the gain A set by the first gain setting unit; a second gain setting unit that sets a gain, B, in response to an instantaneous signal strength of an audio output signal of the first signal amplifying unit; a gain calculating unit that calculates a gain, C n , as a product of gain A and gain B adjusted by a smoothing factor including αC n-1 B, wherein α is selected to be a time constant smaller than or equal to 1 so that the gain C n is smoothly changed; and a second signal amplifying unit that adjusts the signal strength of the audio input signal based upon the gain C n calculated by the gain calculating unit.