1.7 sound & hearing

8/3/2019 1.7 Sound & Hearing

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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


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


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


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


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.

1.7 sound & hearing

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