Question

Which of the following frequencies of sound can’t be heard by human beings?
A. 5Hz
B. 20Hz
C. 400Hz
D. 1000Hz

Answer 1

Hint: The audible range of frequency is from 20 Hz to 20,000 Hz. These are the only frequencies that can be heard by humans. A human ear cannot catch the frequencies, pitch and the amplitude of the sound waves above or below this range.

Complete answer:
Sound travel in a wave has the properties of frequency, amplitude just as the electromagnetic waves or the light waves. The frequency of sound can be measured in Hertz. From the wide range of sound frequencies, there is only a limited range to which humans are audible. This is called the audible range. This audible frequency has the range from 20 Hz to 20,000 Hz.
The sound frequencies that are above the audible range that is above 20,000Hz are called ultrasonic and those that lie below the audible range are called as infrasonic. Bats emit ultrasonic sound waves at very high frequencies. Some animals can hear and also produce infrasonic sound waves.
From the given options, the frequencies that lie in audible range are 20Hz, 400Hz and 1000Hz. And, the frequency of $5Hz$ does not lie in the audible range and it cannot be heard by humans.

So, the correct answer is “Option A”.

Note:
 In audible frequencies, the best range of sound that humans hear is about 1,000 Hz to 5,000 Hz. Ageing can also reduce the number of frequencies of sound a human ear can hear as old age people mostly develop hearing problems. Only sounds of large frequencies and pitch can be heard by them. A healthy and young person can almost hear all the frequencies in the audible range.