NAVODAYA VIDYALAYA SAMITI��CHAPTER – SOUND�CLASS - VIII

BY

PRIYANKA RANA NAIN

TGT SCIENCE JNV RAJGARH M.P.

CONTENT:-

1. INTRODUCTION. 2 •WHAT PRODUCES SOUND ?

3. SOUND PRODUCED BY HUMANS. 4 • PROPAGATION OF SOUND

5. HUMAN EAR. 6 • AMPLITUDE

7. TIME – PERIOD. 8 • FREQUENCY

9. AUDIBLE AND INAUDIBLE SOUND. 10 • NOISE AND MUSIC

11. NOISE POLLUTION

SOUND

• SOUND IS A FORM OF ENERGY PRODUCED BY VIBRATIONS.

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• SOUND PLAY AN IMPORTANT ROLE IN OUR LIFE.

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• IT HELPS US TO COMMUNICATE WITH EACH OTHER.

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• WE HEAR A WIDE VARIETY OF SOUNDS IN OUR SURROUNDINGS.

WHAT PRODUCES SOUND ?��SOUND IS PRODUCED BY A VIBRATING BODY.

VIBRATION :- VIBRATION IS THE TO AND FRO OR BACK AND FORTH MOTION OF AN OBJECT.

EXAMPLE:- •IF YOU STRIKE A SCHOOL BELL, IT VIBRATES AND PRODUCES SOUND.

•IF YOU PLUCK A STRETCHED RUBBER BAND, IT VIBRATES AND PRODUCES SOUND.

MUSICAL INSTRUMENTS

• SOME MUSICAL INSTRUMENTS PRODUCE SOUND WHEN THEY ARE BEATEN OR STRUCK.
• EXAMPLE:- BELL , GHATAM , MANJIRA , JALTARANG ETC.

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MUSICAL INSTRUMENTS AND THEIR VIBRATING PARTS

SOUND PRODUCED BY HUMANS

• IN HUMANS SOUND IS PRODUCED BY THE VOICE BOX OR LARYNX.
• IT IS THE UPPER PART OF THE WIND PIPE.
• TWO VOCAL CORDS , ARE STRETCHED ACROSS THE LARYNX LIVING A NARROW SLIT. WHEN THE LUNGS FORCE AIR THROUGH THE SLIT , IT VIBRATES AND PRODUCE SOUND.

PROPAGATION OF SOUND

• SOUND REQUIRES A MEDIUM TO PROPAGATE.
• SOUND TRAVELS THROUGH SOLIDS , LIQUIDS AND GASES.
• SOUND DOES NOT TRAVEL IN VACUUM.

EXAMPLE:-

• SOUND TRAVELS THROUGH THE SOLID THREAD OF A PAPER CUP TELEPHONE.

• A WHALE LISTEN TO THE REFLECTED SOUND IN WATER TO LOCATE IT’S PREY.

• WE ARE ABLE TO LISTEN SOUND BECAUSE SOUND TRAVEL IN AIR.

HUMAN EARS

• HOW DO WE HEAR SOUND THROUGH OUR EARS ?

• SOUND ENTERS THE EAR THROUGH THE EAR CANAL. IT MAKES THE EAR DRUM TO VIBRATE. THE EAR DRUM SENDS THE VIBRATIONS TO THE INNER EAR. FROM THERE THE SIGNAL GOES TO THE BRAIN , SO WE HEAR THE SOUND.

STRUCTURE OF THE HUMAN EAR

• THE OUTER EAR IS CALLED PINNA WHICH COLLECTS THE SOUND WAVES. THESE SOUND WAVES PASSES THROUGH THE EAR CANAL TO A THIN MEMBRANE CALLED EAR DRUM WHICH START TO VIBRATES.

THE VIBRATIONS ARE AMPLIFIED BY THE THREE BONES IN THR MIDDLE EAR CALLED MALLEUS , INCUS AND STAPS.

FROM THE MIDDLE EAR SOUND WAVE

TRANSMITES TO INNER EAR , WHERE

THE SOUND WAVES ARE CONVERTED

INTO ELECTRICAL SIGNAL BY THE

COCHLEA AND SEND TO THE BRAIN

THROUGH AUDITORY NERVES.

BRAIN THEN INTERPRETS THE SIGNAL AS SOUND.

PROPERTIES OF THE SOUND WAVES

• AMPLITUDE

• FREQUENCY

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• TIME - PERIOD

AMPLITUDE OF SOUND WAVE

• THE MAXIMUM DISPLACEMENT OF AN OSCILLATING BODY FROM ITS MEAN POSITION IS CALLED IT’S AMPLITUDE ( BA OR BC )

OR

• THE AMPLITUDE OF THE SOUND WAVE IS THE HEIGHT OF THE CREST AND TROUGH.
• IT IS REPRESENTED BY THE LETTER “A” .
• S.I. UNIT OF AMPLITUDE IS METRE .

FREQUENCY OF SOUND WAVE

• THE NUMBER OF OSCILLATIONS PER SECOND IS CALLED FREQUENCY.
• IT IS REPRESENTED BY THE SYMBOL √ .
• THE UNIT OF FREQUENCY IS HERTZ (HZ) .

TIME PERIOD OF SOUND WAVE

• THE TIME TAKEN FOR ONE OSCILLATION IS CALLED TIME PERIOD .
• IT IS REPRESENTED BY THE LETTER T .
• THE S.I. UNIT OF TIME PERIOD IS SECOND.
• FREQUENCY AND TIME- PERIOD ARE REPRESENTED AS FOLLOWS :-

. T = 1/ √

√ FOR ONE OSCILLATION :-

√ = 1/ T

LOUDNESS AND PITCH OF SOUND

1. THE LOUDNESS OF SOUND DEPENDS UPON THE AMPLITUDE OF VIBRATION.

• IF THE AMPLITUDE IF LESS THE SOUND IS FEEBLE .

• IF THE AMPLITUDE IS MORE THE SOUND IS LOUD.

• THE UNIT OF LOUDNESS IS CALLED DECIBLE .

2. THE PITCH OF SOUND DEPENDS UPON THE FREQUENCY OF VIBRATIONS.

• IF THE FREQUENCY IS LESS THE SOUND HAS LOW PITCH.

EXAMPLE:- SOUND OF A DRUM , SOUND OF AN ADULT ETC .

• IF THE FREQUENCY IS MORE THE SOUND HAS HIGH PITCH.

EXAMPLE:- SOUND OF A WOMAN , SOUND OF A WHISTLE ETC .

AUDIBLE AND INAUDIBLE SOUND

1. AUDIBLE SOUND IS THE SOUND WHICH WE CAN HEAR.

• IT HAS FREQUENCY BETWEEN 20 HZ TO 20,000 HZ .

2. INAUDIBLE SOUND IS THE SOUND WHICH WE CAN NOT HEAR.

IT HAS FREQUENCY LESS THAN 20 HZ AND MORE THAN 20,000 HZ.

• SOUND WAVES WHOSE FREQUENCY ARE MORE THAN 20,000 HZ IS CALLED ULTRASONIC SOUND.

ANIMALS LIKE DOLPHIN , BATS , DOGS ETC CAN HEAR ULTRASONIC SOUND.

• SOUND WAVES WHOSE FREQUENCY ARE LESS THAN 20 HZ IS CALLED INFRASONIC SOUND.

ANIMALS LIKE ELEPHANTS , WHALE ETC CAN HEAR INFRASONIC SOUND.

NOISE AND MUSIC

1. NOISE :- UNPLEASANT SOUNDS ARE CALLED NOISE.

• IT IS PRODUCED BY IRREGULAR OR NON- PERIODIC VIBRATIONS.

EXAMPLE:- IF ALL THE STUDENT IN A CLASSROOM SPEAK TOGETHER , NOISE IS PRODUCED .

• SOUND PRODUCED BY HORNS OF BUSES AND TRUCKS .

2. MUSICAL SOUND:- SOUND WHICH IS PLEASANT TO EAR IS CALLED MUSICAL SOUND.

• IT IS PRODUCED BY REGULAR OR PERIODIC VIBRATIONS.

EXAMPLE:- SOUND PRODUCED BY MUSICAL INSTRUMENTS.

• SOUND OF A PERSON SINGING A SONG.

NOISE POLLUTION

THE PRESENCE OF EXCESSIVE OR UNWANTED SOUND IN THE ENVIRONMENT IS CALLED NOISE POLLUTION.

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1. CAUSE OF NOISE POLLUTION:- NOISE POLLUTION IS CAUSED BY SOUNDS OF VEHICLES , EXPLOSIONS , SOUND OF VARIOUS MACHINES , LOUDSPEAKERS ETC .

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• IN HOME NOISE POLLUTION IS CAUSED BY TELEVISION , RADIO AND MUSIC SYSTEM AT HIGH VOLUME , SOME KITCHEN APPLIANCES , DESERT COOLER , AIR CONDITIONER ETC.

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HARMFUL EFFECTS OF NOISE POLLUTION

NOISE POLLUTION CAUSES SEVERAL HEALTH PROBLEMS LIKE LACK OF SLEEP , HYPERTENSION , HIGH BLOOD PRESSURE , ANXIETY ETC.

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• A PERSON EXPOSED TO LOUD SOUND CONTINUOUSLY MAY GET TEMPORARY OR PERMANENT IMPAIRMENT OF HEARING.

MEASURES TO LIMIT NOISE POLLUTION

• NOISE POLLUTION CAN BE REDUCED BY USING SILENCER IN VEHICLES , INDUSTRIAL MACHINES AND HOME APPLIANCES .

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• REDUCING USE OF VEHICLE HORNS

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• RUNNING TV , RADIO AND MUSIC SYSTEM AT LOW VOLUME

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• PLANTING MORE TREES ALONG ROAD AND BUILDING SIDES.

THANK YOU

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BY PRIYANKA RANA NAIN

JNV RAJGARH M.P.