Hardware Reference
In-Depth Information
With an audio adapter, a PC can record waveform audio. Waveform audio (also known as
sampled
or
digitized sound
) uses the PC as a recording device (such as a tape recorder). Small computer
chips built into the adapter, called
analog-to-digital converters (ADCs)
, convert analog sound waves
into digital bits that the computer can understand. Likewise, digital-to-analog converters (DACs)
convert the recorded sounds to an audible analog format.
Sampling
is the process of turning the original analog sound waves into digital (binary) signals that
the computer can save and later replay (see
Figure 13.1
)
. The system samples the sound by taking
snapshots of its frequency and amplitude at regular intervals. For example, at time X, the sound might
be measured with an amplitude of Y. The higher (or more frequent) the sample rate, the more
accurately the digital sound replicates its real-life source and the larger the amount of disk space
needed to store it.
Figure 13.1. Sampling turns a changing sound wave into measurable digital values.
Originally, sound cards used 8-bit digital sampling, which provided for only 256 values (2
8
) to
convert a sound. Today's highest-quality sound cards feature 32-bit sampling (2
32
), which translates
into more than four trillion possible digital values that can be matched to a given sound.
You can experiment with the effects of various sampling rates (and compression technologies) by
recording sound with the Windows Sound Recorder (in Windows XP or earlier versions; the sound
