SOUND

MADE BY KRITISH ANTIL CLASS : 9 : D

INDEX

1.PRODUCTION OF SOUND2.PROPAGATION OF SOUND3.CHARACTERISTICS OF SOUND

WAVES4.FREQUENCY5.AMPLITUDE6.SPEED

7. Reflections of sound8. Laws of Reflection of Sound9. Range of hearing10. Application of ultrasound11. Structure of human earS

PRODUCTION OF SOUND•SOUND IS PRODUCED WHEN SOMETHING VIBRATES. THE

VIBRATING BODY CAUSES THE MEDIUM (WATER, AIR, ETC.) AROUND IT TO VIBRATE. VIBRATIONS IN AIR ARE CALLED TRAVELING LONGITUDINAL WAVES, WHICH WE CAN HEAR. SOUND WAVES CONSIST OF AREAS OF HIGH AND LOW PRESSURE CALLED COMPRESSIONS AND RAREFACTIONS, RESPECTIVELY.

PROPAGATION OF SOUND•ORDINARILY, WE HEAR SOUND, TRANSMITTED THROUGH THE AIR.

UNLIKE LIGHT, SOUND CANNOT PASS THROUGH VACUUM. THIS WAS DISCOVERED IN 1654 BY OTTO VON GUERICKE. LET AN ELECTRIC BELL BE ENCLOSED WITHIN A BELL JAR WHICH IS PLACED OVER A DISC. THROUGH A HOLE IN THE DISC, AIR CAN BE REMOVED BY USING A VACUUM PUMP. ON GRADUALLY REMOVING THE AIR, THE SOUND OF THE BELL BECOMES FEEBLER AND BECOMES ALMOST INAUDIBLE WHEN THE LIMIT OF EXHAUSTION IS REACHED. THE REASON WHY ABSOLUTE SILENCE IS NOT ATTAINED, IS THAT THE CONDUCTING WIRES TRANSMIT SOME SOUND.

CHARACTERISTICS OF SOUND WAVES

WE CAN DESCRIBE A SOUND WAVE BY ITS :•FREQUENCY•AMPLITUDE•SPEED

FREQUENCY

•THE RATE PER SECOND OF A VIBRATION CONSTITUTING A WAVE, EITHER IN A MATERIAL (AS IN SOUND WAVES), OR IN AN ELECTROMAGNETIC FIELD (AS IN RADIO WAVES AND LIGHT).•THE STANDARD UNIT OF FREQUENCY IS THE HERTZ .

AMPLITUDE•AMPLITUDE IS THE FLUCTUATION OR DISPLACEMENT OF A WAVE FROM ITS MEAN VALUE. WITH SOUND WAVES, IT IS THE EXTENT TO WHICH AIR PARTICLES ARE DISPLACED, AND THIS AMPLITUDE OF SOUND OR SOUND AMPLITUDE IS EXPERIENCED AS THE LOUDNESS OF SOUND.

SPEED

•THE SPEED OF SOUND IS THE DISTANCE TRAVELLED PER UNIT TIME BY A SOUND WAVE AS IT PROPAGATES THROUGH AN ELASTIC MEDIUM.THE SPEED OF SOUND IS CALLED "MACH 1."

REFLECTIONS OF SOUND•THE REFLECTION OF SOUND IS SIMILAR TO THE REFLECTION OF

LIGHT AS IT FOLLOWS THE LAWS OF REFLECTIONS, WHERE THE ANGLE OF INCIDENCE IS EQUAL TO THE ANGLE OF REFLECTION AND THE INCIDENT SOUND, THE REFLECTED SOUND AND THE NORMAL LIE IN THE SAME PLANE. SOUND BOUNCES OFF THE SURFACE OF SOLID OR A LIQUID LIKE A BILLIARD BALL BOUNCES OFF THE SIDES OF THE TABLE. IN ORDER FOR REFLECTION OF SOUND TO OCCUR, THE SURFACE CAN BE EITHER ROUGH OR POLISHED AND OF CONSIDERABLY LARGE SIZE.

LAWS OF REFLECTION OF SOUND

•THE ANGLE OF INCIDENCE IS ALWAYS EQUAL TO THE ANGLE OF REFLECTION.•THE INCIDENT SOUND WAVE, THE REFLECTED WAVE AND THE

NORMAL AT THE POINT OF INCIDENCE ARE IN THE SAME PLANE.

RANGE OF HEARING•THE RANGE OF HEARING FOR A HEALTHY YOUNG PERSON IS 20

TO 20,000 HERTZ. THE HEARING RANGE OF HUMANS GETS WORSE WITH AGE. PEOPLE LOSE THE ABILITY TO HEAR SOUNDS OF HIGH FREQUENCY AS THEY GET OLDER. THE HIGHEST FREQUENCY THAT A NORMAL MIDDLE-AGED ADULT CAN HEAR IS ONLY 12-14 KILOHERTZ.

APPLICATION OF ULTRASOUND

•ULTRASOUND IS GENERALLY USED TO CLEAN SPIRAL TUBES,ELECTRONIC COMPONENTS ETC.•ULTRAIT IS USED FOR MEDICAL DIAGNOSIS AND THERAPY AND ALSO AS

A SURGICAL TOOL.•SOUND ARE USED TO DETECT CRACKS AND FLAWS IN METAL BLOCKS.

STRUCTURE OF HUMAN EAR

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