Ultrasonic transducer and ultrasonic speaker using the same

An ultrasonic speaker comprising:

• an ultrasonic transducer including:
• a first fixed electrode provided with a plurality of holes;
• a second fixed electrode provided with a plurality of holes substantially corresponding to and facing said plurality of holes provided on said first fixed electrode;
• and
• a vibrating film clamped by at least each surrounding portion of said plurality of holes in said first and said second fixed electrodes and having a conductive layer to which a DC bias voltage applied;
• said plurality of holes provided in said first and said second fixed electrodes are through holes formed by continuous concentric cylindrical holes of at least two different sizes in diameter and depth;
• a signal source which generates signal waves in the audio frequency band;
• a carrier wave-supply unit which generates and outputs carrier waves in the ultrasonic frequency band;
• and
• a modulating unit which modulates said carrier waves according to signal waves in the audio frequency band output from said signal source,
• wherein said ultrasonic transducer is driven by a modulated signal output from said modulating unit and applied between said fixed electrodes and the electrode layer of said vibrating film.