Question

Sound waves having frequencies more than 20,000 Hz are called ………. –

Answer 1

Hint: Sound is a type of energy which the vibrating bodies produce. We have two sound forms - audible and inaudible. Those sounds are graded according to their frequency ranges.

Complete Step-by-Step solution:
Human ears cannot sense sound frequencies below 20 vibrations per second i.e. 20 Hz per second. Therefore, any vibration below that frequency is going to be inaudible to humans. The human ear cannot sense frequencies above 20000 vibrations per second (20 KHz) in the high-frequency range, and the amplitude of the wave will be dependent on the sound's loudness. Therefore, the frequencies below 20 Hz and over 20 KHz fall under the inaudible frequencies band.
The low frequency signal that can't be heard by human ears is also known as infrasonic signal. Whereas the inaudible higher frequency range is also known as ultrasonic sound.
Hence, sound waves having frequency more than 20000Hz are called ultrasonic sound.
Whereas the inaudible higher frequency range is also known as ultrasonic sound.

Additional Information:
The human ear could indeed recognize frequencies between about 20 Hz and 20 KHz with ease. Sound waves with frequencies of between 20 Hz and 20 KHz are considered to be audible vibrations. When they are within audible frequency range, the human ear is receptive to any minute pressure change in the air. This can measure changes in air pressure of less than one billionth. When we people get older and are exposed to sound for prolonged periods of time, our ears are weakened and the upper limit of detectable frequencies decreases. For an average adult middle-aged person, 12-14 kilohertz is the highest frequency they can hear clearly.

Note: Some animals, such as dogs, can hear sounds of frequencies greater than 20 KHz. In certain applications inaudible frequencies are beneficial. Ultrasound devices used to monitor and research several medical problems operate at frequencies above 20 KHz.