PURPOSE: To shorten time required to search a possessed file or the like in dependence upon a tone by modulating an audio frequency signal with an ultrasonic wave and interruptedly outputting this ultrasonic signal to the external through a small-sized speaker.

CONSTITUTION: An audio frequency signal 1-6 generated by an audio frequency signal generating circuit 1-1 is modulated with the ultrasonic signal by a modulating circuit 1-2 and amplified by an amplifier 1-3 and sent to an ultrasonic output speaker 1-4 and sent to the external as an ultrasonic wave. A sound receiver receives this ultrasonic wave 3-7 by a microphone 3-1 and demodulates it by a demodulating circuit 3-3, and an audio frequency signal 3-11 is given to a speaker 3-5 and reaches human ears. Since the ultrasonic signal has the same properties of directivity and attenuation as an acoustic wave, the direction from which the objective tone is heard is discriminated.