A noise reduction circuit for use in an audio signal recording/reproducing apparatus includes a first filter circuit for providing frequency emphasis to a signal supplied thereto; a first signal path connected in series with the first filter circuit, and including a voltage-controlled amplifier for amplifying a signal supplied thereto with controllable gain and a second filter circuit for providing frequency emphasis to the signal passing through the voltage-controlled amplifier; a level detecting circuit for controlling the gain of the voltage-controlled amplifier in response to the level of the signal passing through the voltage-controlled amplifier; a resistor connected to the first signal path for reducing the effect of the frequency emphasis by the second filter circuit when the level of the signal passing through the voltage-controlled amplifier is reduced; and a low pass filter circuit connected with the first signal path for reducing the effect of the frequency emphasis by the first and second filter circuits when the level of the signal passing through the voltage-controlled amplifier is high; wherein the circuit for noise reduction provides a first amount of frequency emphasis for intermediate level signals supplied thereto and a second lower amount of frequency emphasis for low and high level signals supplied thereto. When used in its encoding mode, the first and second filter circuits each include a high-pass filter circuit, and when used in its decoding mode, these filter circuits each include a low-pass filter circuit.