Physics 10 Class Notes CHAPTER NO 11 Chapter NO. 11 SOUND
Table of Contents
How sound is produced, the nature of sound.
How sound is propagated.
Characteristics of sound: loudness, intensity, pitch, quality, music, and noise.
Intensity sound level, it’s unit and formula
Echo, speed of sound.
Noise pollution, the importance of acoustics.
Audible frequency range.
Ultrasound uses of ultrasound.
The solution to problems.
Q1: What is sound? How it is produced; transmitted and received?
The stimulus due to a sounding body capable of producing a sensation of hearing is called sound.
A sound is a form of energy that travels through a medium in the form of longitudinal (or) compressional waves. When sound fall on-ear membrane it produces a sensation of hearing.
Generation of sound:
Three things are necessary for the generation of sound.
i. Vibrating body.
ii. Transmitting medium.
iii. Hearing device.
I. Vibrating body:
A vibrating body produces sound, therefore it is a must. As the body vibrates it does work on the particles of the medium and sets them into vibration.
II. Transmitting medium:
The vibrating body does work on the particles of the medium and set them into oscillations. Thus the vibrating body supplies the energy of its vibrations to the particles of the medium transmits this energy from the source to the receiver using alternate compression and rarefaction.
A device that can detect sound waves is known as a hearing device (or) receiver. The human ear is the best receiver of sound waves, which converts the sound waves into the sensation of hearing.
Besides the human ears other mechanical and electrical devices have been made to detect and analyze the sound waves.
When the sound waves fall on-ear, the energy of sound set the ear membrane of the ear into vibrations. As the ear is connected with the brain, therefore hearing of sound occurs.
Q2: Define the terms loudness, intensity, pitch, and quality of sound. Explain each term by giving examples?
Ans: In fact, there are a few fundamental characteristics of sound by means of which we can distinguish one sound from another sound. The following are the important characteristics of sound
“The magnitude of auditory sensation produced by a sound is known as loudness.” “OR”
“The characteristic of sound by which we can distinguish between a Pc lod and f int sound is known as loudness”
Loudon s directly depends upon the intensity of sound.
ii. Intensity of sound:
The energy transmitted per unit time by a sound wave through unit Varea placed perpendicular to the direction of propagation of waves is known of sound. “OR”
The power delivered by sound waves through the unit area is called the intensity of sound
I = –E—
W/m2is the SI unit of intensity of sound.
Factors on which intensity and Loudness Depends:
The intensity and loudness of a sound depending on the following factors.
a) Amplitude of vibrating Body:
The increase in the amplitude of the vibrating body causes an increase in intensity and loudness of sound. For example, A drum produces a loud sound when its membrane is struck strongly while the sound is faint when the membrane is struck gently.
b) Frequency of vibrating Body:
The increase in the frequency of the vibrating body also causes an increase in the loudness of sound. For example, the sound produce by a thin taut membrane of a drum is louder than the sound produces by the thick loose membrane of a drum.
c) Surface Area of vibrating body:
The increase in the surface area of the vibrating body causes an increase in the loudness of sound. For example, a dhool produces a louder sound as compared with a dholak.
d) Distance between the vibrating body and listener:
The loudness of sound also depends upon the distance from the vibrating body. If the distance between the source and listener INCREASE THEN THE LOUDNESS OF SOUND DECREASE.