Multiple choice

The frequency of (mechanical) longitudinal waves below the audible range is known as _____.

  1. ultrasonic

  2. supersonic

  3. infrasonic

  4. none of these

Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

Infrasonic refers to frequencies below the human hearing range (below 20 Hz). These are mechanical longitudinal waves at very low frequencies. Option C is correct. Ultrasonic (A) is above 20 kHz, supersonic (B) refers to speed, not frequency.