Basis Science Unit 1
Topic- Sound Energy

Sound is a form of wave transferred through an elastic medium from a vibrating body to a listener. When an object vibrates, it disturbs the surrounding air causing waves to travel outward in all direction.
The disturbance travels out from the source if vibration in the form of longitudinal wave.
Sound waves cannot travel through vacuum. A material medium is always required for the passage of sound. The material media are solid, liquid and gas. Sound can e produced by plucking the guitar string, playing musical instruments, rubbing, blowing of whistles. These objects vibrate so vibration is a rapid to and fro motion of an object. Human voice produces sounds due to vibration in the vocal cords.
Sound is measured in Hertz.

Types of Sounds
There are infrasonic sounds and ultrasonic sounds.
A. Infrasonic Sounds; these are sounds that cannot be heard by men. They can be heard by animals like snakes, bats.
The frequency of Infrasonic sounds are below 20 Hertz.

B. Ultrasonic Sounds; Some sounds are within human hearing range of frequency between 400Hz to 20,000Hz

1. Define frequency of sound
2. Give 4 uses of ultrasonic sounds
3. Give 5 examples of musical instruments


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