We can hear sounds, but what are they?
From physics, sound is a vibration that creates a wave in a medium, usually air. A sound has three main properties: pitch, volume, and duration.
Pitch is a musical term for what physics calls frequency. Frequency is how many times the wave vibrates per second and is measured in Hz (Hertz). For example, 1 Hz means one vibration per second. Humans can typically hear sounds between 20 Hz and 20,000 Hz.
Volume is how loud the sound is. It is often confused with pitch because we do not hear every frequency equally well, and higher-pitched sounds can seem louder - up to a point.
Duration is how long the sound lasts.
