EVERYDAY SCIENCE

Detailed explanation-1: -Explanation: The Ultrasound is inaudible to humans as ultrasound frequencies ranges above 20, 000 Hz which is above the audible range. Hence, the normal ear of human beings can not sense the sound above 20, 000 Hz and below 20 Hz.

Detailed explanation-2: -The human ear has a perceived frequency range of 20 Hertz to 20 kHz which is called audible sound. Any frequency below 20 Hz is called infrasound and any frequency above 20 kHz is called ultrasound. These are inaudible sounds. So, we cannot hear inaudible sounds, ultrasound, and infrasound.

Detailed explanation-3: -An ultrasound is not a unique type of sound, therefore, but is classified differently due to the fact that humans cannot hear it. Ultrasounds have a frequency greater than 20 kHz, which is beyond the frequency limit of sounds that humans are able to hear.

Detailed explanation-4: -Sounds having frequency lower than 20 Hz are known as infrasonic sounds and that having frequency greater than 20 kHz are known as ultrasonic sounds. Thus, humans can neither hear infrasonic nor ultrasonic sounds.

Detailed explanation-5: -The Health Protection Agency (HPA) [6] states that high levels of exposure to ultrasound can produce permanent damage to biological tissues. However, at low levels, such as those used in diagnostic testing, they should not produce damage because they do not produce more heat than physiological thermal temperature.