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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.
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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- Spring '14