Basically an sound or audio wave is a 1-D (one-dimensional) pressure or acoustic wave.
When an acoustic wave enters in the ear, then the eardrum vibrates, that causes the inner ear's tiny bores to vibrate along with it, sending the nerve pulses to the brain.
These never pulses are perceived as sound by the listener.
In the similar way, whenever an acoustic wave strikes a microphone then the microphone generates an electrical signal that represents the sound amplitude as a function of time.
The Human ear's frequency range are from 20 to 20000 Hz.