Post on 06-Apr-2018
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1.6 Sound & Hearing
Sound is produced through vibration of
objects
The kinetic energy is changed to soundenergy.
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In space, no one can hear
you scream.WHY?
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Properties of sound
Sound needs a medium to travel
Sound can travel through solid, liquid and gas
(air).
Sound cannot travel in vacuum.
Astronauts in outer space cannot speak directly to each other.
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Properties of sound
Sound travels fastest insolid.
Because solid particles are
arranged closely together.They can pass on thevibrations quickly.
Sound travel slowest ingas.
Because gas particles arevery far apart.
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Properties of sound
When switch is turned on, the electric bell vibrates & the
ringing sound can be heard.
Once vacuum pump is turned on, the air is slowly
removed. As this happens, the sound gets weaker until itcannot be heard at all.
Bell jar
INFERENCE: Sound cannot be heard in vacuum because no air
particles is present to pass on the vibration.
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ACTIVITY 1.6
To in
vestigate the properties of sound
1. Strike the tuning fork on a rubber bung & place
it near your ear.
2. Listen & observe what happened
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ACTIVITY 1.6
To in
vestigate the properties of sound
1. A tuning fork is struck with a metallicobject.
2. Hold it inside a pan filled with water.
3. Observe what happened.
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1. Sound can be reflected into different direction byhard and smooth surfaces. Eg: concrete walls, glass
& metal.
2. Sound can be absorbed by soft and rough surfaces.Eg: carpets, curtains, soft board & sponge.
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Reflection & absorption of sound
3. Reflected sounds are called echoes.
4. Hard & smooth surface reflect sound well.
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5. Ships fitted with echo-sounder are able to
determine the depth of the water.
Reflection & absorption of sound
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ACTIVITY 1.6
To in
vestigate the properties of sound
Materials: Styrofoam, cloth.
Procedure
1. The apparatus as
shown is set up.
2. Try to hear theticking sound of the
stopwatch (without
materials).
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ACTIVITY 1.6
To in
vestigate the properties of sound
Procedure
3. Place a piece of
styrofoam on the table.
Listen to the ticking
sound of the stopwatch.
4. Replace the styrofoam
with a cloth. Listen &
compare the ticking
sound with what heard
in step 2 & 3.
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ACTIVITY 1.6
To in
vestigate the properties of sound
Question
1. How is sound produced?
2. What can you conclude about sound from activity
B?
3. Name the process in which sound is bounced back
from a surface.
4. Which material absorbs more sound, the table
surface or styrofoam?
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Limitations on Hearing
As we grow old the ear drumbecomes less sensitive.
Devices that helps us to hear
a) Stethoscope to hear softsound of our heart beat
b) Loud speaker amplify the
soundc) Hearing aid rectifies defect
in hearing
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Stereophonic hearing
Involves the use of two ears to listen
Stereophonic hearing help us to detect the direction
of a sound. When a sound comes from the right, our right ear
detects the sound slightly earlier than left ear.
The sound heard by right ear is louder than left ear.