Question

Some whistles are designed to produce waves that can attract the attention of dogs but humans do not notice these waves. What kind of waves are these?

• A. These are normal sounds waves whose frequency is less than $20Hz$. Humans cannot hear them because these waves have frequencies below the audible range.
• B. These are normal sounds waves whose frequency is more than $20,000Hz$. Humans cannot hear them because these waves have frequencies above the audible range.
• C. These are electromagnetic waves.
• D. These are supersonic sound waves.

Answer 1

The correct option is B These are normal sounds waves whose frequency is more than $20,000Hz$. Humans cannot hear them because these waves have frequencies above the audible range.

A dog whistle (also known as a silent whistle or Galton's whistle) is a type of whistle that emits sound in the ultrasonic range, which most humans cannot hear but some other animals can, including dogs and domestic cats, and is used in their training.