In digital recording, the analog signal of sound is translated into a stream of discrete numbers, representing the changes in air pressure over time; thus producing a sample of the original sound. Now let’s take a look of how to do digital recording and how digital recording work.
General digital recording processes are as below:
1. The input device creates analog signal.
2. The analog signal is transmitted to an analog-to-digital converter (ADC).
3. The ADC translates this signal to a series of binary numbers.
4. These numbers are transmitted via cables into storage, such as a hard drive or CD burner.
Playback processes of digital recording are as below:
1. The numbers are transmitted from storage into a digital-to-analog converter (DAC).
2. The DAC translates the numbers back to an analog signal.
3. The signal is amplified and transmitted to the loudspeaker. And we hear the sound of digital recording.
The sample rate is very critical for doing digital recording. If the sample rate is too low, the sampled signal cannot be reconstructed to represent the original sound signal. And the output sound quality of the digital recording will be floppy or noisy.
To avoid this problem happen to digital recording, the sound signal shall be sampled at a rate at least twice that of the highest frequency component in the signal.
In digital recording, sampling frequencies are generally divided into 22.05 KHz, 44.1 KHz and 48 KHz.
22.05 KHz FM radio can only reach the voice quality, 44.1 KHz can render CD-quality sound, 48 KHz is better than this. Frequency higher than 48 KHz is beyond humane being’s hearing capacity, basically, it’s meaningless for digital recording.
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