infrasonic frequency

2.17  infrasonic frequency. Frequency less than 20 Hz, the nominal lower range of human hearing. Unit, hertz (Hz).

Annotation 1          The term “infrasonic” may be used to indicate a device or system intended to operate at an infrasonic frequency.

Annotation 2          The frequency range is often that between 1 Hz and 20 Hz when physiological effects are discussed.