Britannica Sources used in this answer

How do ultrasonic waves differ from sounds that humans can hear?

Created from Britannica articles using AI. AI can make mistakes, so verify using Britannica articles.

Understand the concept of sonoluminescence which is a phenomenon of turning sound into light — ultrasonics Learn how collapsing bubbles with sound can create sonoluminescence.

The primary difference between ultrasonic waves and sounds audible to humans is their frequency. While human hearing is generally limited to a range of approximately 20 to 20,000 hertz (20 kilohertz), ultrasonics refers to vibrations and waves with frequencies exceeding this upper limit.123

Because these frequencies are too high for the human ear to detect, they are classified as ultrasonic. In contrast, audible sound waves fall within the range that the human auditory system can perceive, which is characterized by a nonlinear response to both intensity and frequency.32

While humans cannot hear these high-frequency vibrations, many animals—such as bats, dolphins, and certain rodents—possess the ability to perceive sounds well into the ultrasonic range. Beyond their frequency, ultrasonic waves are utilized in various practical and scientific applications, including ultrasonic cleaning, ultrasonic machining, and research into phenomena like cavitation and sonoluminescence.145