Chapter 13 – Sound
● What is sound?
Sound is those vibrations that travel either through the air or another medium and at the same time can be hear d when they reach a person's or animal's ear.
● Musical Sound: The sound which leads a pleasing effect on the ear.
● Noise: The sounds which cause a jarring or an unpleasant effect.
● Types of Sound:
(i) Audible Sound: Those vibrations whose frequency lies between 20 Hertz to 20,000 Hertz (20 kHz) can be easily heard by human ear.
(ii) Inaudible Sound: Sounds that has frequencies either above 20,000 Hertz or below 20 Hertz cannot be heard by the normal human ear.
● The low frequency sounds which cannot be heard by ear are known as infrasonics whereas the high frequency sounds which cannot be heard are known as ultrasonics.
● The vibration of the vocal cords in human beings produces sound.
● Sound requires a medium to travel. This medium could be gas, liquid or solid but it cannot travel through the vacuum.
● The eardrum in the ear are receptor of the vibrations of sound. It further sends those vibrations to the inner ear. From there, these signal are carried to the brain and interpreted as sound.
● Higher or unwanted sounds leads to noise pollution. Noise pollution can lead to serious health problems in human beings. For example, Lack of sleep, high blood pressure, anxiety and many other health disorders could be consequences to noise pollution. A person who is continuously exposed to a loud sound can get either temporary or even cause permanent impairment of hearing.
How can we manage noise pollution?
● We should try to reduce noise pollution.
a. In air craft engines, transport vehicles, industrial machines and home appliances, silencing devices must be installed.
b. Planting more trees on the roadside and in parks can also reduce noise pollution.
● Amplitude: It is the maximum extent of vibration of the vibrating body from its mean position.
● Time Period: One complete to and fro movement of the pendulum around its mean position is one oscillation and the time taken by any vibrating particle to complete its one oscillation is known as time period.
● What is the frequency?
It is the number of vibrations produced by the vibrating body in one second.
SI unit of frequency:- hertz (Hz).
● What are the characteristics of Sounds?
1. Loudness: The vibrations produced in the ear which allow us to distinguish between a loud and a faint sound. The larger is the amplitude of vibration, the louder is the sound. Loudness of sound is directly proportional to the square of the amplitude.
2. Pitch: The characteristics of sound that make a difference between a shrill sound and a soft sound. The higher the frequency of vibration is, the higher is the pitch.
3. Quality: It is the characteristic that allows distinguishing between musical notes emitted by different musical instruments or voices even though they have the same pitch and loudness.