Infrasonic sound is of frequency

Infra-sound: it is a low-frequency sound and is a sound that is lower in frequency than 20 Hz (hertz), the basic limit of human hearing. Hearing becomes slowly less sensitive as frequency decreases, so for humans to perceive infrasound, the sound pressure should be sufficiently high. The ear is the important and primary organ for sensing infra-sound, but at huge intensities it is possible to feel infra-sound vibrations in various parts of the body. So, the Infrasonic sounds are of frequency 20 Hz and below.