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LESSON NOTES
Introduction to sound

Sound is a form of energy which gives us the sensation of hearing.
Sources of sound

1. Chirping of birds
2. People talking to each other.

3. Sound of utensils at home

4. Airplane flying
Production of sound

Sound is produced by Vibration of an object. We produce sound due to the vibration

of our voice box/ larynx.

How does sound travel?
 In order to propagate, sound requires a medium through which it can travel.
This medium could be a gas, liquid or solid.
 Sound propagates in a medium as the particles of the medium vibrate from a
starting point. This means that sound always has a starting point and an ending
point.

 For instance, while you talk to a friend, as you speak, the particles in the air get
displaced due to the pressure caused by the sound you produce. They then
displace the adjacent particles and so on. In this way, sound travels from your place
to your friend’s ears.

 Therefore, we can say that the particles of a medium do not travel from one point
one another in order to propagate sound. Sound propagates because of the
disturbance caused by a source of sound in the medium.

Introduction to waves

A wave is a disturbance in a medium which moves from one point to another and
carries energy without a net movement of particles. It may take the form of variation
of pressure.

E.g.: Rubber cork on the water that goes up and down when a rock falls in the water
creates a ripple.

A stone when thrown inside a still water causes ripple formation.

Sound is called a mechanical wave as it needs medium for propagation

How can sound travel through air?