Class 8 Sound Notes
Class 8 Sound Notes
Sound is a form of energy which produces a sensation of hearing in our ears.
A kind of rapid to and fro motion of an object is called vibration.
- Sound is produced by vibrating objects.
- This motion is also known as Oscillatory motion.
Voice Box :-
Upper end of the windpipe, below the hard part on the throat is called the voice box.
It is the passage for the inlet and outlet of air in the lungs.
In humans, the sound is produced by the larynx.
A wave is a disturbance that moves through a medium when the particles of medium set neighboring particles into motion.
- Sound needs a material medium to propagate.
Wave length (λ) :-
The distance between two consecutive compressions or two consecutive rarefactions is called wavelength.
- S.I. unit:- metre (m)
Frequency (ν) :-
The number of oscillations made by a vibrating body per unit time is known as frequency.
- Frequency = Total number of oscillations/Total time taken
- S.I. unit:- Hertz (Hz)
Time period (T) :-
The time taken by a vibrating body to complete one oscillation is known as time period.
- Time period = Total time taken/Total number of oscillations
- S.I. unit:- Second (s)
Frequency = 1/Time Period
ν = 1/T Or, T = 1/ν
Amplitude (A) :-
The magnitude of the maximum disturbance in the medium on either side of the mean value is called the amplitude of the wave.
How the brain interprets the frequency of an emitted sound is called its pitch.
- Pitch of a sound is determined by its frequency.
The measure of the response of the ear to the sound is called loudness.
- Loudness of a sound is determined by its amplitude.
A thin membrane which is stretched tightly to receive the waves of sound at the end of ear canal.
Unpleasant sounds are called noise.
Sound which are pleasant for us is known as music.
A sound of single frequency is called Tone.
Sound of several frequencies is called Note.
Audible and Inaudible Sounds :-
- The range of audible frequencies in Human Ears is roughly from 20 to 2000 Hz.