Nature of Sound Waves

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NATURE OF SOUND WAVES 

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OBJECTIVES 

 At the end of the lesson, you should be able to:

a. Explain how sound waves are produced,

transmitted, and propagated;b. Perform activities related on the nature of sound 

 waves;

c.  Appreciate the things around us which act as media for sound waves; and 

d. Point out the importance of sound waves.

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SOUND WAVES 

Sound waves are produced by vibrating 

objects.

How are sound waves produced?

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This refers to the to-and-fro oscillation of molecules as a disturbance travels

through a medium.

VIBRATION OF MOLECULES 

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WHEN WE SAY OSCILLATION,

Consider a pendulum..

How does a pendulum move?

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The Grandfather’s Clock is

also a good example of a 

 pendulum.

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Like the pendulum, vibrating molecules also

 move back and forth; thus, disturbing theother molecules.

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RECALL THE TYPES OF WAVES 

Transverse Wave 

Longitudinal Wave 

Under what type of wave aresound waves classified?

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Molecules of the transverse wave move up and 

down.

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Molecules of the longitudinal wave move back 

and forth.

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Sound waves are considered longitudinal waves.

To illustrate it further, moving a slinky back and 

 forth is a perfect example of showing longitudinal 

 waves.

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Since sound waves are longitudinal waves, the

 vibration of the molecules will be parallel tothe direction of the wave propagation.

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How is your voice produced?

The sound that comes from your mouth when 

 you speak is produced by the vibrations of twothin sheets of membrane which is called your 

 vocal cords.

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What is the key word on howsounds are produced?

Vibration (of molecules)!

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How are sound waves transmitted?

Sound waves are transmitted thru a medium 

or media.These include gas (air), liquid (water), and 

solid.

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Will there be a difference on how

sound waves will travel on thethree media?

 Assign a member of your table to put his/her 

ear against the end of a tabletop. Another one

has to gently tap the other end of the table with a ruler or pencil.

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Are all solids good transmitters of

sound waves?

Strike the tuning fork and bring its handledown on the cloth. Then strike again the

tuning fork and place its handle on the

tabletop. Which is louder?

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Solids that are not good in transmitting sound 

do not possess much elasticity; therefore they are poor media for sound transmission.

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Generally, liquids are better conductors of 

sound than gases.

Which of the two is a better sound

transmitter: liquids or gases?

Example

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So why is liquid a better sound

transmitter than gas, and solidbetter than the liquid?

 Arrangement of molec ules i  n solids, liquids,

and  gases 

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How sound waves travel

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That is why you need to speak louder as you 

climb a mountain..so that you can be heard. 

Which of the three is the best fortransmitting sound?

Solid/s!

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How are sound waves propagated

or spread?

 As the sound waves are transmitted in solids,

liquids, and gases, sound waves also spread or  propagate at the same time.

So when they spread, molecules disturb other  molecules.

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 And because sound waves are longitudinal 

 waves, this disturbance happens continuously 

 until the air molecules (sound waves) strike

 your eardrums, making it vibrate.

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 And thru the parts of your ear, impulse is sent 

to your brain which is then interpreted assound.

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Why do you hear sounds?

Because of the propagation or

spreading of sound waves!

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Can sound waves travel thru a

vacuum?

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What are the practical

importances of sound waves?

Bats rely on sound waves to locate their prey and avoid 

 predators.

Bats use echolocation to locate and catch their prey. When bats fly, they produce a constant stream of high-pitched sounds that only bats are able to hear. When the sound  waves produced by these sounds hit an insect or other 

animal, the echoes bounce back to the bat, and guide them 

to the source.

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IN GENERAL..

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Let us see to it that before wetransmit issues, we clarified it

first. That way, it doesn’tpropagate; and you avoid hurting

the person involved. 

LESSON LEARNED?

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SOUND WAVES AND THEIR SOURCES 

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FOR YOUR ASSIGNMENT:

Do an advance reading on the speed of sound 

in different media.Page 369 of your book.

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Thank you for listening!

Good day!