7 audio mixers are used to combine multiple channels

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Unformatted text preview: ed in kilohertz (KHz) am its typical values are 8, 11, 22, and 44.1 KHz. For example, the sampling rate of CD-quality audio is 44.1 KHz, and that of telephone-quality audio is 8 KHz. 2. Quantization. Quantization determines the digital measured value of the analog waveform at the sampling time. The larger the range of numbers used for quantization, the more gradations of the digitally sampled waveform can be represented, resulting in better quality audio. Quantization is measured in terms of number of bits and its typical values are 8, 12, and 16 bits. Figure 19.4 illustrates sampling and quantization of an analog signal. In Figure 19.4(a), the analog signal is sampled at periodic points in time. The sampled values are then represented by the closest quantization levels. The difference between the value of the closest quantization level and the real analog value is known as quantization error. In Figure 19.4(b), 2 bits are used to represent quantization, resulting in 4 possible levels, and in Figure 19.4(c), 3 bits are used, allowing 8 quantization levels. As the number of bits used to represent quantization increases, more quantization levels become possible resulting in reduced quantization error and increased audio quality. 3. Number of channels. It refers to the number of channels used for audio recording. Its typical values are one for mono systems, two for stereo systems, and 5.1 for Dolby surround-sound systems. The quality and the storage and bandwidth requirements of digital audio depend on the three parameters discussed I above. The higher the sampling rate, the more bits used to represent quantization, and the more channels, the better the quality of the digital audio, and the higher the storage and bandwidth requirements. For example, an 8 KHz sampling rate, 8 bits quantization, and mono recording will produce telephone-quality audio, and will require a bandwidth of 8000 x 8 x 1 = 64 Kb/s. On the other hand, a 44.1 KHz sampling rate, 16 bits quantization, and ster...
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