Sound is a form of energy. Sound is the quickly varying pressure wave within a medium.
Sound is produced by the vibration of objects. When object vibrate, they move backwards and forwards very quickly. Frequency is the number of vibrations in one second. Frequency is measured in hertz (Hz).If the frequency is 100Hz, it means that it produced 100 vibrations every seconds.
The medium affect the speed of sound. Thus it will also affect the sound.
The examples of stuff producing sound are instruments, insects, phones, human talking, music from CD player, sound of the fan, traffic noise and alarm clock.
Sound travels in the form of waves. Sound travels through matter (solids, liquids and gases). Sound toke time to travel from one place to another. The speed of the sound in the air is about 330 metres per seconds.
We can also find things with sound. For example, if we make a loud noise in a large room, there will be echo. The sound we make travels to the walls and is reflected back to our ears. Echoes are also able to find objects underwater. This is called echolocation.
Some uses of echolocation is to find submarines from surface ships, to measure the depth of the sea and to find shoals of fish in fishing boats. Animals like bats and dolphins also use echolocation to find food and where they are going.
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Textbook Resource: Explore Your World With Science Discovery 2.
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