Question

Infrasonic sound is of frequency

• A. below $20Hz$
• B. above $20Hz$
• C. below $20kHz$
• D. above $20kHz$

Answer 1

The correct option is A below $20Hz$

Infra-sound is a low-frequency sound. It is sound that is lower in frequency than 20 Hz (hertz) or cycles per second, the normal limit of human hearing. Hearing becomes gradually less sensitive as frequency decreases, so for humans to perceive infrasound, the sound pressure must be sufficiently high. The ear is the primary organ for sensing infra-sound, but at higher intensities it is possible to feel infra-sound vibrations in various parts of the body.
Hence, the Infrasonic sound is of frequency 20 Hz and below.