Sound – where does it come from?

sound_where_does_it_come_from

A sound is created when the particles in a medium (usually air in our world) are set moving and forced out of a state of rest. This happens, for example, when we speak. Our vocal chords produce audible pressure variations (high and low pressure) in the air. Sound travels in air at a speed of approximately 340 metres per second. It spreads like a wave and is a mechanical vibration.