Sound is a form of energy produced by vibrations that travel in waves through a medium such as air, transferring energy from one place to another without transferring matter. Vibrations cause particles in the air or other medium to vibrate, bumping into nearby particles and transferring the vibrations in a domino effect. The pitch of a sound depends on the frequency of vibration - higher frequencies produce higher pitches and lower frequencies produce lower pitches. For sound to be heard, it requires a medium such as air to travel through, as it cannot travel through a vacuum.

1. SCIENCE - SOUND
Bhavishya Gaur – 8th H

2. WHAT IS SOUND?
Sound is
 A form of energy made by vibrations.
 When an object vibrates it causes the air
particles around it to move.
 These particles bump into particles close to
them and this continues until they run out of
energy.

3. TRY THIS:
 Put your finger on your
neck and say “aah” as loud
as you can.
 Now say it as soft as you
can.
 You can not only hear the
sound, but youcan feel the
vibration inside your throat.

4. HOW SOUND TRAVELS?
 Sound passes through
the medium as
longitudinal waves.
 When the vibrations
are fast you hear a
high pitch. When
they’re slow, you
hear a low pitch.

5. HOW SOUND TRAVELS?
 Sound is produced due to the vibration of objects.
 Vibration is the rapid to and fro motion of an object.
 Eg :- The sound of human voice is produced due to the
vibration of the vocal cords.
 A stretched rubber band when plucked vibrates and
produces sound.

6. HOW SOUND TRAVELS?
 Activity :- Strike the prongs of
a tuning fork on a rubber pad
and bring it near the ear.
 We can hear a sound. If a
suspended table tennis ball is
touched with the vibrating
prong, the ball is pushed away
repeatedly. This shows that the
prong is vibrating and vibrating
objects produces sound

7.  The pitch of sound (shrillness or flatness)
depends on the frequency of vibration.
 If the frequency is high, the sound has high
pitch and if the frequency is low, the sound
has low pitch.
LOW SOUND AND HIGH SOUND

8.  High pitch = High frequency
 Low pitch = low frequency
LOW SOUND AND HIGH SOUND

9.  Sound is a mechanical wave and
needs a medium for propagation.
 Sound travels through solids, liquids
and gases. Sound does not travel in
vacuum
SOUND NEEDS MEDIUM TO TRAVEL

10. Activity:-
 Suspend an electric bell in an air tight
bell jar.
 Connect the bell jar to a vacuum pump. If
the switch is pressed, we can hear the
sound of the bell.
 If air is pumped out through the vacuum
pump, we cannot hear the sound of the
bell.
 This shows that sound needs a medium
to travel and sound cannot travel in
SOUND NEEDS MEDIUM TO TRAVEL

11.  Volume control
 Loudness
 Strength of the wave ( measured in db
“decibels”) Energy of the wave
AMPLITUDE OF SOUND

12.  It depends on the
type of instrument.
There are four
types.
 Woodwind
 String
 Percussion
 Brass
DO YOU KNOW HOW DOES
MUSICAL INSTRUMENT CREATE SOUND

13. BRASS INSTRUMENT
 Brass instruments
make music by
buzzing lips while
blowing.

14. HOW DOES VIOLIN PRODUSES
SOUND?
Sound is
 The body of the violin is a large
hollow chamber that functions as a
speaker or amplifier for vibration.
 The strings are suspended above
the body of the instrument by a
bridge, a small maple piece of
wood secured to the top of the
instrument by the tension of the
strings.
 The vibration from the strings is
transferred through the bridge to
the body of the instrument where

15. HOW DOLPHINS COMMUNICATE
EACH OTHER
 One way they do it is by making sounds. They don’t have
vocal chords like we do, but they can control muscles in their
blowholes to make different noises.
 Some of the noises they make sound like whistles and
squeaks. Some of their sounds are ultrasonic, which means
they are too high in pitch for people to even hear!
 By making all these sounds, dolphins can identify themselves
to each other.

16. NOISE POLLUTION
 Sound that is unwanted or disrupts one’s quality of life is called
as noise.
 When there is lot of noise in the environment, it is termed as
noise pollution.
 Sound becomes undesirable when it disturbs the normal
activities such as working, sleeping, and during conversations.
 It is an underrated environmental problem because of the fact
that we can’t see, smell, or taste it.
 World Health Organization stated that “Noise must be
recognized as a major threat to human well-being”

17. HEALTH EFFECTS
 According to the USEPA, there are
direct links between noise `and
health. Also, noise pollution
adversely affects the lives of
millions of people. Noise pollution
can damage physiological and
psychological health.
 High blood pressure, stress
related illness, sleep disruption,
hearing loss, and productivity loss
are the problems related to noise
pollution.
 It can also cause memory loss,
severe depression, and panic

18. SOURCES OF NOISE POLLUTION
 Transportation systems are the main source of
noise pollution in urban areas.
 Construction of buildings, highways, and streets
cause a lot of noise, due to the usage of air
compressors, bulldozers, loaders, dump trucks,
and pavement breakers.
 Industrial noise also adds to the already
unfavorable state of noise pollution.

19. SOLUTION FOR NOISE POLLUTION
 Planting bushes and trees in and around sound
generating sources is an effective solution for
noise pollution.
 Regular servicing and tuning of automobiles can
effectively reduce the noise pollution.
 Buildings can be designed with suitable noise
absorbing material for the walls, windows, and
ceilings.
 Workers should be provided with equipments
such as ear plugs and earmuffs for hearing
protection

20. HUMAN VOICE BOX
 In humans sound is produced by the voice box
or the larynx.
 The voice box is at the upper part end of the
windpipe.
 Tow vocal cords, are stretched across the
voice box or larynx in such a way that it leaves
a narrow slit between them for the passage of
air

21. VOICE BOX OF HUMAN

22. THANK-YOU!
Bhavishya Gaur – 8th H