Question

what is ultrasound?
sound produced above frequencies that we can hear.
sounds that are very slow moving.
sound produced by sources that also produce ultrasonic light.
sound produced below frequencies that we can hear.
rewatch

Explanation:

Ultrasound is defined as sound waves with frequencies higher than the upper limit of human hearing (typically above 20,000 Hz). The first option states "Sound produced above frequencies that we can hear," which matches this definition. The second option is incorrect as ultrasound is about frequency, not speed. The third option is incorrect as ultrasound is a sound, not related to light. The fourth option describes infrasound (frequencies below human hearing).

Answer:

A. Sound produced above frequencies that we can hear.