Sound waves consist of vibrating molecules, thus they need a medium (air or another material) by which they can travel. When they reach the ear, they make the eardrum vibrate into the inner ear where they are converted into electrical signals which pass to the brain
Sound waves are a type of longitudinal wave; the molecules vibrate in the same direction as the energy transfer.
The speed of sound in air is 330 m/s. It changes by temperature of the air, and sound travels fastest in solids and slowest in gases.
Greater amplitude = louder sound, and greater frequency = higher pitch.
Sound waves can be reflected, as with all waves. The reflection is called an echo
The approximate range of audible frequencies for a healthy human ear is 20 Hz to 20 000 Hz
Longitudinal waves consist of compressions and rarefactions by which they can move. Without these they cannot move.
Period = number of seconds for one vibration, and frequency = number of vibrations per second. f = 1/T; it is measured in hertz. 1 Hz = one vibration/second
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Experiment to determine the speed of sound in air
There are 2 microphones separated by at least 3-4 metres, connected to a timer, in a straight line
Bang 2 wooden blocks together. The 1st microphone activates the timer and the 2nd one stops it
The speed is calculated from the distance between the 2 microphones and the time taken by the sound to travel between them.
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