Sound of frequency below 20 Hz known as _________.

CONCEPT:

• Supersonic speed: An object moving with a speed greater than the speed of sound is said to move with a supersonic speed.

Frequency can be divided into three categories based on their frequency range:

• Audible sound waves: The frequency range of this wave is 20Hz - 20000Hz. Humans can easily detect these types of waves.
  • Example: Sound produced by Vocal cords.
• Infrasonic waves: The frequency range of these types of waves is below 20Hz. Humans cannot detect it.
  • Example: Sound produced by Earthquake, Volcanic eruption and ocean waves, etc.
• Ultrasonic waves or Ultrasound waves: The sound frequency above 20,000Hz or 20 kHz is known as ultrasonic waves. Humans cannot detect it too. 

EXPLANATION:

• Infrasonic is the sound waves having a frequency of less than 20 Hz. So option 1 is correct.