LEVEL ADJUSTING CIRCUIT, DIGITAL SOUND PROCESSOR, AUDIO AMP INTEGRATED CIRCUIT, ELECTRONIC APPARATUS AND METHOD OF AUTOMATICALLY ADJUSTING LEVEL OF AUDIO SIGNAL

摘要

Level adjusting circuit for adjusting level of input audio signal, includes: N filters, N being integer of two or more; N dynamic range compression (DRC) circuits corresponding to N filters; adder; (N−1) band pass filters corresponding to crossover frequencies of N filters; and (N−1) gain correcting units corresponding to (N−1) band pass filters. Each filter receives and passes input audio signal through its respective set band. i^th (1≦i≦N) DRC circuit amplifies signal from i^th filter and adjust its gain to prevent level of its output signal from exceeding threshold level. Adder adds each of output signals of DRC circuits. j^th (1≦j≦N−1) band pass filter passes band including crossover frequencies of j^th and (j+1)^th filters from output signal of adder. j^th gain correcting unit adjusts at least one of gains of j^th and (j+1)^th DRC circuits based on level of output signal of j^th band pass filter.