Patent ID: 8774426

Claim:
A signal processing apparatus, comprising: a high frequency component extracting circuit configured to extract a high frequency component higher than a first specific frequency from an audio signal; a low frequency component extracting circuit configured to extract a low frequency component lower than a second specific frequency from the audio signal; a first adjusting circuit configured to amplify a level of the high frequency component with a first gain; a second adjusting circuit configured to amplify or attenuate a level of the low frequency component with a second gain; an accumulating circuit configured to accumulate the high frequency component adjusted with the first adjusting circuit and the low frequency component adjusted with the second adjusting circuit; a high frequency level detecting circuit configured to detect the level of the high frequency component adjusted with the first adjusting circuit; a low frequency level detecting circuit configured to detect the level of the low frequency component adjusted with the second adjusting circuit; a first control circuit configured to control the first gain according to the level of the high frequency component detected with the high frequency level detecting circuit so that the first adjusting circuit amplifies the level of the high frequency component to a target level; and a second control circuit configured to control the second gain according to the level of the high frequency component and the level of the low frequency component so that a difference between the level of the high frequency component adjusted with the first adjusting circuit and the level of the low frequency component adjusted with the second adjusting circuit becomes smaller than a specific level determined in advance, wherein said second control circuit is arranged to control the second gain so that the second adjusting circuit attenuates the level of the low frequency component with the second gain smaller than the first gain by a first value determined in advance when the level of the high frequency component detected with the high frequency level detecting circuit is equal to the target level and the level of the low frequency component detected with the low frequency level detecting circuit is greater than the target level, and said second control circuit is arranged to control the second gain so that the second adjusting circuit attenuates the level of the low frequency component with the second gain smaller than the first gain by a second value greater than the first value when the level of the high frequency component detected with the high frequency level detecting circuit is smaller than the target level.