Patent ID: 8036398

Claim:
An audio signal processing circuit comprising: a first filter including, a counter arranged to receive periodicity information synchronized with periodicity of a periodic noise included in an input signal and to convert the periodicity information to delay information, a variable delaying unit configured to receive the delay information from the counter and to carry out delay processing so as to delay a level adjusted signal supplied thereto by an amount of time determined on the basis of the delay information, and a filter unit configured to receive the input signal, the filter unit having a notch characteristic at a frequency f, the frequency f satisfying f=N/T, where N represents an integer equal to or greater than one and T represents a delaying time applied by the delaying unit, in which the level adjusted signal is supplied to the variable delaying unit from the filter unit; a second filter including, an adaptive filter unit configured to output a pseudo noise signal approximating the periodic noise on the basis of the periodicity information, and a subtraction unit configured to subtract the pseudo noise signal from the input signal; and a switching unit configured to switch between outputting a first output from the first filter and a second output from the second filter and to output either the first output or the second output, the switching unit outputting the first output from the first filter at a time when the periodicity of the periodic noise changes and during a predetermined time after the time when the periodicity of the periodic noise changes.