Facts At Your Fingertips: Energy and forces – Sound
Sounds are vibrations that we hear with our ears. The vibrations travel through substances such as air or water in the form of sound waves.
When the waves reach our ears, they make our eardrums vibrate. The size and shape of the waves determine the kind of sound we hear.
High and low
The number of vibrations a sound wave makes every second is called its frequency.
The higher a sound’s frequency, the higher its pitch, or note. Some animals, such as dogs, can hear sounds with a very high pitch that humans cannot hear. Elephants can hear very low-pitched sounds.
Using sounds
Sound waves bounce off hard objects. We hear sound bouncing back at us as an echo. Some animals, such as dolphins and bats, use echoes to detect prey.
They emit high-pitched sounds and listen out for any echo bouncing back off objects around them.
Sound quality
The quality, or timber, of a sound is determined by the shape of its wave.
Each instrument in an orchestra has a different timber. Some, such as a flute, produce sound waves with a regular shape, which we hear as a pure note.
Others, such as drums, make rougher sounds with irregular waves.
Loud and soft
The more energy a sound wave contains, the larger its amplitude. We hear sounds with lots of energy as loud sounds. A sound’s loudness is measured in decibels. Decibels are measured on a special scale called a logarithmic scale.
A sound measured at 20 dB is 10 times louder than one measured at 30dB.