- Sound is a form of energy created by vibrations that travel in waves and is transmitted through a medium such as air, water, or other materials. - For sound to be produced, an object must vibrate and transfer that vibration to nearby air particles or another medium; this causes a longitudinal pressure wave that propagates away from the source. - The pitch of a sound depends on the frequency of vibration, with higher frequencies producing higher pitches and lower frequencies producing lower pitches. Sound needs a medium and cannot travel through a vacuum.

2. 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 you
can feel the vibration inside your throat.

3. 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.

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.
High Pitch Low Pitch

5. PRODUCTION OF SOUND
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.
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.
Vibrating
tuning fork
Table tennis
ball
Thread

6. LOW SOUND AND HIGH SOUND
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.

7. • High pitch =
high frequency
• Low pitch =
low frequency

8. SOUND NEEDS MEDIUM TO TRAVEL
Sound is a mechanical wave and needs a medium for propagation.
Sound travels through solids, liquids and gases. Sound does not
travel in vacuum.
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 vacuum.
Cork
Bell jar
Electric bell

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

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

11. WOODWIN INSTRUMENTS
• Woodwinds make music by blowing on the
top of the instrument or on a reed.

12. STRING INSTRUMENTS
• Strings make music by plucking or
strumming the strings.

13. PERCUSSION INSTRUMENTS
• Percussion instruments make music by
striking, shaking or scraping them.

14. BRASS INSTRUMENT
• Brass instruments make music by buzzing
lips while blowing.

15. HOW DOES VIOLEIN PRODUSES
SOUND?
The body of the violein 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 the sound is then
amplified.

16. 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.

17. Whales sing
to each
other.
Sound travels
through water

18. 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”

19. 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
attacks.

20. 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.
• Loud speakers, plumbing, boilers, generators, air
conditioners, fans, and vacuum cleaners add to the
existing noise pollution.

21. 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.

22. SOLUTION FOR NOISE POLLUTION
• Similar to automobiles, lubrication of the
machinery and servicing should be done to
minimize noise generation.
• Soundproof doors and windows can be installed
to block unwanted noise from outside.
• Regulations should be imposed to restrict the
usage of play loudspeakers in crowded areas
and public places.
• Factories and industries should be located far
from the residential areas.

23. SOLUTION FOR NOISE POLLUTION
• Community development or urban
management should be done with long-
term planning, along with an aim to
reduce noise pollution.
• Social awareness programs should be
taken up to educate the public about the
causes and effects of noise pollution.

25. 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

26. VOICE BOX OF HUMAN

27. Sound travels to your ear
Sound
The air vibrates
but does not travel from
the alarm to the ear.

28. HUMAN EAR
The outer ear called pinna collects the sound
waves. The sound waves passes through the ear
canal to a thin membrane called eardrum. The
eardrum vibrates. The vibrations are amplified by
the three bones of the middle ear called hammer,
anvil and stirrup. The middle ear then transmits
the sound waves to the inner ear. In the inner ear
the sound waves are converted into electrical
signals by the cochlea and sent to the brain
through the auditory nerves. The brain then
interprets the signals as sound.

30. Mobile phones use radio
Sound - electrical signal - radio signal - electrical signal - sound
Radio signal
Mobile
phone
beacons
In the second
phone the radio
signal is changed
into an electrical
signal then into
sound.
In one phone the
sound is changed
into an electrical
signal then into
a radio signal.
Sound - electrical signal - radio signal - electrical signal - sound

31. TELEPHONES
The message travels through miles of wires
as an electrical signal.
microphone
loudspeaker
electrical signal

33. Sound travels 4 times faster through water than
through air.
There is no sound in space.
Geologists use their knowledge of how sound
travels through rocks to help them find oil fields.
Whales in the ocean "sing" to each other. The
sound of their song can travel a distance of
800km.
Sound moves through the air at 340m per
second.
SOME INTRESTINGFACTS