Question

Which of the following correctly represents the increasing order of frequency for infrasound, ultrasound, and audible sound?

• A. Infrasound $<$ Audible $<$ Ultrasound
• B. Ultrasound $<$ Audible $<$ Infrasound
• C. Audible $<$ Ultrasound $<$ Infrasound
• D. All sounds are of the same frequency

Answer 1

The correct option is A Infrasound $<$ Audible $<$ Ultrasound

Sound can be classified broadly into three categories based on its frequency:

• Audible sound: The range of frequency audible to humans - $20\text{Hz}$ to $20\text{kHz}$.
• Infrasound: The range of frequency $<20\text{Hz}$.
• Ultrasound: The range of frequency $>20\text{kHz}$.

Therefore, audible sound lies in between infrasound and ultrasound, i.e. Infrasound $<$ Audible sound $<$ Ultrasound.