Patent ID: 8483407

Claim:
A noise reducing circuit for a sound reproducing apparatus including a sound signal switching section which switches a sound signal so that a level difference appears in an output signal waveform of the sound signal, a low-cut filter which is disposed at a downstream of the sound signal switching section and has a cutoff frequency for cutting off a low frequency range of the sound signal, an electroacoustic transducer which outputs a sound based on the sound signal, and a switching instructing section which instructs switching of the sound signal switching section, the noise reducing circuit comprising: a variable low-cut filter which is disposed at an upstream of the sound signal switching section and has a variable cutoff frequency; and a control circuit which controls the cutoff frequency of the variable low-cut filter to a first cutoff frequency being lower than the cutoff frequency of the low-cut filter when a switching instruction is not issued from the switching instructing section, and increases the cutoff frequency of the variable low-cut filter to a second cutoff frequency being higher than the first cutoff frequency when the switching instruction is issued from the switching instructing section, wherein the switching of the sound signal switching section is executed after a predetermined period elapses since the switching instruction is issued, and the control section decreases the cutoff frequency of the variable low-cut filter to the first cutoff frequency from the second cutoff frequency after the switching of the sound signal switching section is completed.