Sound is caused by the vibration of particles but not all vibrations can be heard as sound. Common ideas about sound come from the limited range of vibrations that human ears can detect.
Sound waves are longitudinal waveA wave that moves in the same direction as the way in which the particles are moving. waves.
They cause particles to vibrate parallel to the direction of wave travel.
The vibrations can travel through solids, liquids or gases.
The speed of sound depends on the medium through which it is travelling.
When travelling through air, the speed of sound is about 340 m/s.
Sound cannot travel through a vacuumA volume that contains no matter. because there are no particles to carry the vibrations.
The ear
The human ear detects sound.
Sound waves enter the ear canalThe tube that runs from the outer ear to the eardrum. and cause the eardrum to vibrate.
Three small bones transmit these vibrations to the cochleaPart of the inner ear that contains nerve endings that transmit sound vibrations to the auditory nerve. .
This produces electrical signals which pass through the auditory nervePart of the inner area that carries sound impulses from the cochlea to the brain. to the brain, where they are interpreted as sound.