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

Draw a simple frequency line in your mind from very low to very high values.

1. From about 20 Hz to 20000 Hz sits the audible band, the range a healthy human ear can pick up.
2. Anything below 20 Hz sits below this band. Waves in this low zone are called infrasonic waves.
3. Anything above 20000 Hz sits above the band. Waves here are called ultrasonic waves.

The question asks about frequency below 20 Hz, which places it clearly in the infrasonic zone, so option B is correct. Audio sound refers to the audible band itself, not below it, so option A does not fit. Supersonic is a term used for the speed of an object relative to the speed of sound, not for a range of sound frequency, so option C does not apply. Ultrasonic sits above 20000 Hz, the opposite end of the scale, so option D is also wrong.