Abstract: An intake silencer of the variable type is for reducing noise generated coming from the difference between the inner pressure and the outer pressure of a combustion chamber when an intake valve being opened or closed. The present invention for reducing noise comprises a signal processing part, a signal comparing part and a valve driving part. In the signal processing part, a RPM sensor modulates a waveform obtained by detecting the revolution number of the engine and a F/V converter changes it thereafter emitting a signal to the signal comparing part. In the signal comparing part, a plurality of comparators emit the opened and closed signal to a valve driver by comparing a output signal emitted from the signal processing part with a basic signal. In the valve driving part, when the corresponding valve driver turns on or off by virtue of the signal emitted from the corresponding comparator, a corresponding actuator opens or closes the corresponding valve dividing the inside of the side branch.