Question

Sound of frequency below 20 Hz is called

• A. Audio sounds
• B. Infrasonic
• C. Supersonic
• D. Ultrasonic

Hint:

Compare the given frequency to the 20 Hz to 20000 Hz range that humans can hear.

Answer 1

The Correct Option is B

The human ear can normally detect sound frequencies roughly between 20 Hz and 20000 Hz. This range is called the audible or audio range.

Sound waves with frequency below 20 Hz fall outside this audible range on the lower side. Such waves are called infrasonic waves. Events like earthquakes, volcanic eruptions, and the calls of elephants often produce infrasonic sound.

Option A is wrong because audio sounds refer to the frequency range that humans can actually hear, which starts at 20 Hz, not below it.

Option C is wrong because supersonic describes a speed greater than the speed of sound, which is a completely different concept from wave frequency.

Option D is wrong because ultrasonic refers to frequencies above 20000 Hz, which is the upper end beyond human hearing, not the lower end.

The correct answer is infrasonic.