Why do we use digital audio?

Audio is analogue so why change it?

Related Pages

Try these next ...

• Analogue to Digital
• Storage
• Digital to Analogue
• High Resolution

 

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Overview

Audio is Analogue!

There's no getting around the fact that audio, or 'sound', is analogue. What we hear in the real world with our ears, is vibrations in the air, that our ears interpret as sound. The air moves in a constant and flowing way, that is to say an analogue motion. It is infinite in its form and function. In our efforts to transport sound from one place to another we have to store information about the sound and then reproduce it someplace else.

In electrical terms, sound is an analogue waveform when it leaves the microphone, that is to say a varying voltage. This needs to be stored somehow and reproduced with the least modification, or the most accurate result. When sound was first recorded the recording methods used would mimic the waveform of the audio. On an LP vinyl record the grooves vary their depth according to the analogue wave, and on magnetic tape the strength of the magnetic field varies with the audio waveform.

In theory this is fine, but unfortunately the system has noise and imperfections which mean the reproduced sound - whilst very close - is not quite as good as the original. Every component in the signal path, like electronic circuits, or cables have an effect on the analogue wave. The more the signal is processed the worse the imperfections get. If you try to copy the audio, then its even harder to maintain the original, and it deteriorates through each copy generation.

In the early '80s when Philips and Sony invented the compact disc they looked at storing the audio in a new way, or 'Digitally'. Once they had perfected their system it led to many new possibilities, and then when computers became prevalent the possibilities became even better.

The idea is that as soon as possible after the audio becomes an electrical signal, it is converted into a series of numbers that represent the size and shape of the wave. Once this has happened, these 'numbers' can be transported on a CD or other medium with no loss or modification. Computers too can store and manipulate the 'numbers' with no effect on the data. Using this method we have 'Digital Audio' and this data can stay digital right up to the last possible part of the reproduction chain before being turned back to analogue for our ears.

To find out how this all works in more detail see the pages on Analogue to Digital ( A to D ) and Digital to Analogue ( D to A ), as well as 'Storage'.