Question

What kind of sounds have the frequency of 50 Hz ?

Answer 1

Hint : The unit of frequency is called Hertz (Hz). Human ears with normal hearing can hear sounds between 20 Hz -20,000 Hz and this range is called an audible range of sounds , the sound which has greater frequency than 20,000 Hz are ultrasound.

Complete step by step solution :-
The audible frequency range of sound for the human ear is from 20 Hz to 20,000 Hz .
The frequency of 50 Hz lies in the interval of 20 Hz to 20,000 Hz so this is an audible sound.
Humming sound produced in the mains power house or transmission lines, is associated with alternating current which is twice the frequency of the mains electricity. The fundamental frequency of this sound is usually double of fundamental 50 Hz or 60 Hz depending upon the local power supply line frequency.
This sound has heavily harmonic content when the frequency is above 50-60 Hz.
Electric humming sound may be also heard coming from powerful electric power grid equipment such as utility transformers , caused by mechanical vibrations induced by magnetostriction in the magnetic core.
In magnetostriction physical dimensions of the material changes due to the pressure caused by magnetic fields produced in the iron core.
The vibration of materials magnetization due to the applied magnetic field changes the magnetostrictive strain until reaching its saturation value.
The effect of Magnetostriction was first discovered by James Joule in 1842.Magnetostriction causes energy losses due to frictional heating in susceptible material such as ferromagnetic cores . The effect of magnetostriction is also responsible for the low pitched humming sound that can be heard coming from transformers , where oscillating AC currents produce a changing magnetic field.

Note:-
Generally the humming sound can be easily heard near transformers which is caused due to stray magnetic fields and also due to the phenomenon of magnetostriction, in which the iron core of the transformer changes shape due to the pressure exerted by the magnetic field. The notes of a 4-string bass guitar have many notes between the limit of 50 Hz -100 Hz.