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When a sound signal from a microphone or on a tape needs to be read into a computer, it is digitized, which means that it is sampled and quantized.
Sampling is the discretization of the time domain of the signal: each second of the signal is divided up into 44100, 48000 or 96000 slices (or any other suitable number), and a sample value is associated with each slice. For instance, a continuous 377-Hz sine wave is expressed by
| x(t) = sin (2π 377 t) |
If the sampling frequency (or sample rate) is 44100 Hz, this sine wave will be sampled at points spaced Δt = 1/44100 second apart, and the sample values will be
| xi = sin (2π 377 (t0 + i Δt)) |
where t0 is the time after which sampling begins. Δt is called the sample period.
Quantization is handled in the next section (§1.2).
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