Analogue to Digital

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• Sampling Rates
• Resolution
• Digital to Analogue

 

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Sampling

To understand how we convert analogue audio into digital audio we first need to understand what digital is. Digital data is numbers. Simple as that, a list of numbers that represent something. In the case of digital audio then numbers represent the size of an audio wave at a particular point.

Sampling

Consider the wave in the picture. If we are looking at an electrical audio signal, we can measure the size of the wave at any given point. That measure is called the amplitude, and it is a sample of the wave at that point. To record the wave digitally we take lots of samples in a space of time, and the process is called sampling. Its very simple, but its configuration can have a huge effect on the quality of the recorded data.

 

 

Samples of the audio wave are taken at continuous timed intervals, and the results are stored as digital numbers. These numbers represent the wave's shape and are the 'Digital Audio'. The numbers can be stored as they are and used to re-create the wave when going back from digital to analogue at a later date

 

The two parameters that affect the digital recording are the sampling rate, and the resolution.

Sampling Rate

The sampling rate is the number of samples that are taken in a period of time to record the signal. If we look at the Compact Disc for example, the sampling rate is 44100 samples per second. On DAT the standard rate is 48000 samples per second.
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Resolution

The resolution of the recording refers to the amount of data used for each sample, or rather the accuracy of the sample. Considering the varying wave, you can see that we have to measure the wave from its high point to its low point, and the accuracy can be thought of as how fine a measurement we take. Using Compact Disc again as an example, the resolution is 16-bit. In digital data that means the value of each sample can be anywhere from zero to 65535 ( which is 2 to the power of 16, hence 16-bit ).
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