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NATURE AND PRODUCTION OF
• A form of energy
• By sound, we commonly mean the
vibrations that travel through air and
can be heard by humans.
• Produced by vibrating sources placed
in a medium. (solid, liquid or gas)
THE MEDIUM OF TRANSMISSION
• Any medium that has
particles that can vibrate
will transmit sound.
• Solids can transmit sound
fastest followed by liquid
In olden days, people would hear the
ground for movement.
SOUND CAN BE PRODUCED BY:-
• Vibrating strings
• Vibrating air columns
• Vibrating membranes
• Vibrating plates
SOUND CAN BE PRODUCED BY HUMANS
• The human beings produce
sound by using the voice box
which is called ‘larynx’.
• The voice box contains two
ligaments known as
Sound is produced by
vibrations of these.
WORKING OF VOCAL CORDS
• THE LUNGS PASS A CURRENT OF AIR
BETWEEN TWO VOLCAL CORDS.THIS MAKES
THE VOCAL CORDS VIBRATE.AND THE
VIBRATING VOCAL CORDS PRODUCE
SOUND.WHEN THE MUSCLES ATTACHED TO
THEM CONTRACT AND STRETCH ,THE VOCAL
CORDS BECOME TIGHT AND THIN AND
SOUND IS PRODUCED.
PROPAGATION OF SOUND…
• By saying that sound needs a
medium for propagation , we mean
that sound needs a solid ,liquid ,gas
for transmission sound cannot
travel through vacuum because
vacuum has no molecules which can
vibrate and carry sound waves.
Solids can transmit sound fastest
followed by liquid then air.
PARTS OF EAR…
• Outer ear : The outer part of ear is
funnel shaped to receive the sound waves
.It is called pinna and it is attached to
about 2-3 cm.long passage called ear
• Middle ear : There are 3 small bones
called hammer,anvil and stirrup in the
middle part of ear.
• Inner ear : The inner part of ear has a
coiled tube called cochlea.one end of
cochlea is connected to middle part of ear
through the elastic membrane over the
CHARACTERISTICS OF SOUND…
• FREQUENCY : The number of vibrations
per second is called frequency.It is
expressed in the units hertz(Hz).Frequency
determines pitch of sound.
• PITCH FREQUENCY
• The very low frequency
Sound produced by a
Vibrating pendulum can
Not be heard by our ears.
• AMPLITUDE : The max. diplacement
of a vibrating molecule from its mean
position is defined as amplitude.It is
measured as a distance of crest and
trough of wave. SI unit is metre.
• AMPLITUDE LOUDNESS
• Loudness of sound is the square of
• WAVELENGTH : It is the distance
b/w two neighbouring compressions
of vibrating molecules . More the
sound waves produced every sec.
closer will be the `compressions or
lower will be the wavelength.
SPEED OF SOUND…
• Iron or steel
SPEED OF SOUND
• 340 m/sec
• 1500 m/sec
• 5000 m/sec
Sound travels at a slow speed but
light travels much faster than sound.
AUDIBLE AND NON -AUDIBLE
For human ears, the audible range of
sound waves lies between 20-20,000Hz.
Sound waves less than 20 Hz are called
infrasonic waves and more than 20 Hz
are caleed ultrasoinic waves.thes are not
audible to us.
Many animals make sounda that we cannot
hear as the frequencies they produce or
hear infrasonic sounds of 12 Hz
frequency ,whereas some animals like
dogs,cats,mice etc.can hear and produce
AUDIBLE RANGE OF SOUND FOR
• Upto 40,000
• Upto 1,00,000
• We are familier with many
musical instruments.All the
instruments produce sound by
vibration.on the basis of
vibrating parts ,musical
instruments are classified into
• Guitar,sitar,violin,and sirangi re some
common string instruments.In
these,metal strings of specific length
and thicknes are made to vibrate to
produce sound.the pitch of sound is
altered by changing the tightness of
string.these instruments also have an air
chamber,which also vibrates to increase
the loudness of sound produced
armonica,etc.are some wind
instrumentssound is produced by
vibrating air column inside the
instrument.the pitch of sound is
changed by changing the length
of vibrating column.
e some of the percussion
instruments.in all these
instruments,specific hollow shaped
body is closed by stretched skin of
animals.the stretched skin is beaten
by hands or sticks to vibrate
it.vibrating skin vibrates the column
of air inside the body of the
instrument and sound is
produced.pitch of sound is altered to
a certain extent by decreasing or
• Piano and harmonium are keyboard
instruments.under each key there
is a hole of specific shape and
size,covered with a thin mettalic
stripe .ehen key is pressed
,metallic stripe vibrates and
produce sound of a particular
note.air pressure is changed In
harmonium to produce variety of
MUSIC:All of us enjoy listening
music .any sounds which is
smoothing ,refreshing and
pleasant is called musical sound.
NOISE: Any sound which is
unpleasant ,unwanted or causes
discomfort,may be form of
musical instrument,is called
Sustained pressure of
excessive unwanted and harmful
noise in the env.is called noise
pollution.major sources of noise
pollution are sounds from vehicles
including trains and
aircrafts,machines in factories,horns
loudspeakers,sources of noise pollution
are t.v and musicc player playing at
• It cause annoyaance,irritation,loss of
• It causes sleep
eading to cardiovascular diseases.
• Continuous exprosure to noise over a
period of time or sudden expossure to
loud noise may damage eardrums and
cause permanent loss of hearing.
• Use of loudspeakers should be
avoided in any case.
• Volume of music systems, t.vs
etc.should be kept low,sow that
others should not get disturbed
• Noise producing industries.should be
set-up away from residental areas.
• Use of horns should be minimized
• Donot buy cracker which produce
• Total hearing impairment which is
rare,is ussually from birth
itself.parential diability is ussually
due to a disease,injury or aging.a
deaf child is ussually dumb or have
defective speech as speech develops
as a result of hearing.children with
impaired hearing need special
care.There are many private and govt
institutes to help such persons and to