sound class 9

2. INDEX
1. PRODUCTION OF SOUND
2. PROPAGATION OF SOUND
3. CHARACTERISTICS OF SOUND WAVES
4. FREQUENCY
5. AMPLITUDE
6. SPEED
7. Reflections of sound
8. Laws of Reflection of Sound
9. Range of hearing
10. Application of ultrasound
11. Structure of human earS

3. 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.

4. 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.

5. CHARACTERISTICS OF SOUND WAVES
WE CAN DESCRIBE A SOUND WAVE BY ITS :
•FREQUENCY
•AMPLITUDE
•SPEED

6. 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 .

7. 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.

8. 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."

9. 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.

10. 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.

11. 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.

12. 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.

13. STRUCTURE OF HUMAN EAR