Making Pure Sounds with a Digital Audio Recorder
Almost all modern audio recordings are in digital format. The compact disc (CD)
is the most popular form of commercial audio but it is not the only format for
digital sound. Other digital formats include digital audio tape (DAT), the
MiniDisc and DVD. No matter what format is used for storing the audio, a digital
audio recorder must be used to capture the sound.
The big challenge in digital audio is converting analog signals to digital.
Sound waves in nature are analog - that is, they form a continuous wave pattern.
Digital audio, on the other hand, tries to reproduce and analog waveform with
the use of discrete numbers, creating a jagged wave. The quality of the digital
audio recorder depends in a great part on its ability to capture analog
waveforms accurately and translate them into digital numbers.
The analog-to-digital converter (ADC) converts sound into a series of binary
numbers. The amount of numbers recorded per second is called the sample rate.
The higher the sample rate the closer the digital waveform matches the analog
waveform. The most common sample rate used by any digital audio recorder is
44,100 hertz which is the playback rate used by CD players.
Digital audio is also affected by the number of bits used to represent each
wave. More bits used to capture the waveforms results in a more accurate sound
signal with less distortion. Audio intended for CDs is recorded with 16 bits by
the digital audio recorder.
A modern digital audio recorder can capture audio at 192,000 hertz sample rates
and 24 bits, although the only mediums for storing this kind of audio data are
DVDs or computer hard drives. High-resolution digital audio, though, seems ready
to take over the marketplace and may soon become the new norm.
In order to store digital audio on CDs or DVDs, a laser is used to burn tiny
pits into the plastic. A weaker laser is used to read the pits from the disks,
after which the data has to be converted into analog with a DAC (digital to
analog converter). Although the digital audio recorder may capture all the audio
data, the playback medium may have some errors due to the physically tiny pits
on the disk. For this reason, some kind of error correction scheme must be used
to provide uninterrupted playback.
Some people say the digital audio lacks the warmth of analog audio. It is true
that digital audio will never capture the exact analog signal, but as digital
audio recorders increase their sample and bit rates, the difference between
digital and analog become smaller and smaller.
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