Is 20 Hz high or low frequency?

Sound at 20-200 Hz is called low-frequency sound, while for sound below 20 Hz the term infrasound is used.

High frequency sound is sound of which the frequency lies between 8 and 20 kHz . High frequency sound with a frequency over 16 kHz can hardly be heard, but it is not completely inaudible. High frequency sound and even ultrasound in the lower frequency zone (up to 24 kHz) can be audible if the sound level is high enough.

The human ear can hear frequencies up to 20kHz but we can’t scream higher than 3kHz or so. The bottom end of our hearing range is 20Hz, which is still just below the deepest notes that most of us normally make (around 85Hz).