Question

define audible Infra and ultrasonic sound​

Answer 1

A longitudinal wave whose frequency is above the upper limit of audible range i.e. 20 kHz, is called ultrasonic sound.

A longitudinal elastic wave whose frequency is below the audible range i.e. 20 Hz, is called an infrasonic sound.

Answer 2

Hey mate!

Your answer-

Audible sound: Sounds of frequencies in range of 20 Hz to 20,000 Hz.

Infrasound: It is referred to as low frequency sound. It has frequency lower than 20 Hz.

Ultrasonic sound: Sounds of frequencies more than 20,000 Hz.

Hope this helps ✌