Abstract: A sound multiplex broadcast receiver wherein a SAP channel for a subchannel carrier wave audio signal is provided independently of a channel for the main audio signal to demodulate the subchannel audio signal by way of a noise reduction circuit. The receiver comprises a frequency characteristics correction circuit for correcting the frequency characteristics of the demodulated subchannel audio signal by diminishing the gain at a specific frequency where the distortion factor of the noise reduction circuit reaches a peak, and a noise detection circuit for detecting the level of noise in the audio signal received. The amount of correction by the correction circuit is controlled by the output of the noise detection circuit which varies with the intensity of electric field received, permitting the noise reduction circuit to produce a SAP signal output with flat frequency characteristics.