Audio Engineering: Know It All

Chapter 16. Compact Disc

16.1. Problems with Digital Encoding

16.1.1. Quantization Noise

Although a number of ways exist by which an analogue signal can be converted into its digital equivalent, the most popular, and the technique used in the CD, is the one known as “pulse code modulation,” usually referred to as “PCM.” In this, the incoming signal is sampled at a sufficiently high repetition rate to permit the desired audio bandwidth to be achieved. In practice, this demands a sampling frequency somewhat greater than twice the required maximum audio frequency. The measured signal voltage level, at the instant of sampling, is then represented numerically as its nearest equivalent value in binary coded form (a process which is known as “quantization”). ...