Analog vs Digital

Sound reaches your ears as an analogue signal: the air pressure rises and falls smoothly and continuously, so the wave has a height at every single instant. A computer cannot store a signal like that directly, because its memory and storage hold everything as binary — patterns of 1s and 0s. Analogue sound must therefore be converted into digital form before it can be saved, played back or processed.

Analogue and digital compared

An analogue signal changes smoothly, so between any two points on the wave there is always another point. A digital signal is a list of separate, exact values written in binary, with nothing stored in between.

Why the wave must be converted

The processor can only compare and calculate with 1s and 0s, and storage can only hold those patterns. A continuously changing wave has no gaps in it where a number could be written, so the computer measures the height of the wave at regular intervals instead, storing each height as a binary number. That measuring is called sampling.

Imagine recording a blackbird singing on a tablet. The microphone turns the changing air pressure into a changing voltage, an analogue copy of the song. The tablet measures that voltage again and again and writes each height down as a binary number, so the saved file is a long list of numbers. The speaker later turns those numbers back into movement, following the song.

Because the wave is only measured at certain moments, the digital file is an approximation of the original: the shape of the wave between one measurement and the next is never stored.