Perception of Ultrasound

Ultrasonic vibrations can be perceived as audible sounds when a piezoelectric transducer is pressed against certain areas of the human body. In the range of frequencies investigated (20 to 108 kcy/sec), the threshold of perception seemed to lie near the threshold of feeling (about 10-4 watt/cm2), and the perceived audible sound appeared to be between 8 and 9 kcy/sec, as judged by six test subjects. The threshold of perception and the perceived frequency appear to be dependent upon the hearing characteristics of the individual.