Explanation :
The number of oscillations per unit time is called a frequency of the wave. Its SI unit is Hertz or Hz. It is equivalent to per second.
The hearing range of human ear is 20 Hz - 20,000 Hz. The sound frequency range varies for different animals.
For example, the hearing range of dolphins or bats is up to 1,00,000 Hz. Another example is elephants whose hearing range is 14 Hz to 16 Hz.