Abstract: Regarding that the suppression frequency of LC audio periodic noise suppressor is hard to adjust and the cost of digital audio periodic noise suppressor is high,a novel periodic noise suppressor is designed,in which the periodic noise is selected and enlarged through a RC series-parallel frequency-selective network with adjustable center frequency and scaling circuit.The amplitude and phase of the periodic noise is adjusted to be equal to the periodic noise signal which contains in the audio signal,and then the original audio signal subtracts the selected and amplified periodic noise through a subtraction circuit.The feasibility is proven through theoretical analysis,circuit simulation and prototypical experiment.It is shown that not only the suppression frequency is adjustable in audio frequency range,but also the structure is simple,the cost is low,and the practical effect is good.It is especially suitable to suppress the periodic noise of the sound system in theater,singsong house,assembly hall and family and so on.