Patent attributes
Provided is a buzzer that sounds without noise contamination. Specifically, an inaudible frequency signal generation unit 22 generates an inaudible frequency pulse signal P0; an audio frequency signal generation unit 26 generates, from the signal P0, an audio frequency pulse signal P1: a signal synthesizing unit 28 generates a synthesized frequency pulse signal P2 having the signal P0 in an ON time of the signal P1; a first duty ratio setting unit 30 sets a duty ratio Di of the signal P0 in the signal P2 to gradually increase over a first predetermined period of the signal P2, and thus generates a buzzer driving signal P3; and a buzzer driving unit 40 makes a buzzer 60 sound with a pitch corresponding to a frequency of the signal P3 and volume corresponding to the duty ratio of the signal P3.
