SOUND

NATURE AND PRODUCTION OF SOUND

Sound is…..• 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)

PRODUCTION OF SOUND…

• Sound is produced by vibrating objects.

• For example: ringing of a bicycle bell.

THE MEDIUM OF TRANSMISSION

• Any medium that has particles that can vibrate will transmit sound.• Solids can transmit sound fastest followed by liquid then air.

Application:

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 vocal cords. 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.

STRUCTURE OF EAR…

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 canal.

• 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 oval window. Cochlea is filled with a liqiud.

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 canNot 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 sound vibration.

• 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… MATERIAL• Air• Water• 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 SOUNDS

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 ultrasonic sounds

AUDIBLE RANGE OF SOUND FOR SOME ANIMALS

ANIMALS• Dogs • Cats • Elephants• Mice• Dolphins• Moths

RANGE• Upto 40,000• 100-60,000• 12-20,000• 1000-

1,00,000• Upto

1,00,000• 1000-

2,40,000

MUSICAL INSTUMENTS

• 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 following groups:::

STRING INSTRUMENTS…

• 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

WIND INSTRUMENTS…

• Trumpet,shehnai,flute,bassons,harmonica,etc.are some wind instuments.in these instrumentssound is produced by vibrating air column inside the instrument.the pitch of sound is changed by changing the length of vibrating column.

PERCUSSION INSTRUMENTS…

• Tabla,drum,dholak,bongo,congo,etc.are 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 increasing the tension in the membrane.

KEYBOARD INSTRUMENTS…

• 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 sounds.

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 noise.

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 high volume etc.

HARMFUL EFFECTS…• It cause

annoyaance,irritation,loss of concentration,insomania,etc.

• It causes sleep disturbances,stress,hypertension,etc.leading 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.

CONTROL MEASURES…• 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 loud noise.

HEARING IMPAIRMENT…

• 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 educate parents.

THANK YOU…