{SOUND}

MADE BY :PRATIKSHA YADAV

Class : 9th

Contents• Introduction

• propagation of sound

• wave

• types of wave

• characteristics of sound wave

•frequency

• amplitude

• speed

• Reflection of sound

• reverberation

•Range of hearing

•SONAR

•Human ear

introduction

Sound is a form of energy which produces a sensation of hearing

in our ears.

Propagation of sound

Sound is transmitted by particles (atoms or molecules) in a solid, liquid or gas colliding

with each other. It is a wave which is created by vibrating objects and propagated through a

medium (solid, liquid or gas) from one location to another.

WaveThe disturbance created

in a medium ( solid , liquid , gas ) .

Types of wave Longitudinal waves – the wave in which the particles of medium vibrates to and fro in the same direction in which wave is moving.

Transverse wave – the wave in which the particles of medium vibrates up and down to the direction in which the wave is moving .

Frequency Amplitudespeed

Characteristics of a sound wave

Frequency• The frequency is the

number of wave created Per second is called frequency .

Amplitude

Amplitude is the magnitude of change in the oscillating variable with each oscillation within an oscillating system.

Speed

The speed of sound depends on the medium the waves pass through .

State state substance Speed in m/ssolids Iron 5950

steel 5960liquids Water (sea) 1531

Water (distilled)

1498

Gases air 346oxygen 316

• Multiple reflection of sound is the process in which sound waves bounces off

obstacles and reflects many times before reaching the destination. this is the

phenomena that occurs in a stethoscope. sound waves reflect through the

tube many times before reaching the ears of the doctor. It is very helpful in

detecting problems.

Reflection of sound

Reverberation • Reverberation is the persistence

of sound in a particular space after the original sound is removed. A

reverberation, or reverb, is created when a sound is produced in an enclosed

space causing a large number of echoes to build up and then slowly

decay as the sound is absorbed by the walls and air. 

Range of hearing

• Hearing range usually describes the range of frequencies that can

be heard by an animal or human, though it can also refer to the range of levels.

In humans the audible range of frequencies is usually said to be 20 Hz (cycles per second) to

20 kHz (20,000 Hz) .

SONARSonar stands for sound navigation and ranging .Sonar is a device that uses ultrasonic waves to measure the distance , direction and speed underwater objects .

Human earThe ear is the anatomical organ that detects sound. It not only acts as a receiver for sound, but also plays a major role in the sense of balance and body position. The ear is part of the auditory system.

[MCQs]

A sound wave travels from east to west, in which direction do the particles of air move?(A) East – west (B) North - south(C) Up and down (D) None

. In which medium sound travels faster ?(A) Solid (B) Liquid(C) Gas (D) None

What is the name of short duration wave?(A) Pulse (B) Frequency(C) Time period (D) Velocity

What is the velocity of sound in water at room temperature?(A)1500 m/s (B) (B) 330 m/s(C) 1500 km/s (D) 330 km/s

The unit of quantity on which pitch of the sound depends is :(A)Hertz (B) meter(C) meter/second (D) second

The unit of quantity on which loudness of found depends is :(A) meter (B) Hertz(C) meter/second (D) second

Nature of sound wave is :(A) transverse (B) longitudinal(C) electromagnetic (D) seism

Pitch of high frequency sound is :(A) high (B) low(C) zero (D) infinite

Voice of a friend is recognized by its :(A) Pitch (B) quality(C) Intensity (D) velocity

Sound waves in air are :(A)Longitudinal waves (B) Radio waves(C) Transverse waves (D) Electromagnetic waves

1-A 2-A 3-A 4-A 5-A 6-A 7-B 8-A 9-B 10-A