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The primary disadvantage of MIDI is that the quality of the music a
listener hears will vary depending on the MIDI equipment the listener is
using. For example, MIDI usually sounds much better on an expensive
synthesizer than it does on an inexpensive sound card.
Digital Audio
Digital audio is a simple way to record and play sounds of any type. It
works like a tape recorderÑyou record something, then later play it
back. Digital audio stores the sound as a long series of numbers.
Sound Waves
Sound waves are vibrations in the air. Sound waves are generated by
anything that vibrates; a vibrating object causes the air next to it to
vibrate, and the vibration is passed through the air in all directions.
When the vibrating air enters your ear, it makes your eardrum vibrate,
and you hear a sound. Likewise, if the vibrating air hits a microphone, it
causes the microphone to vibrate and send electrical signals to whatever
it's connected to.
These vibrations are very fast. The slowest vibration frequency you can
hear is about 20 vibrations per second, and the fastest is around 16,000
to 20,000 vibrations per second.
Recording Digital Audio
To record digital audio, your computer monitors the electrical signal
generated by a microphone, an electric guitar, or another source. At
equal intervals of time (for CD-quality sound, this means 44,100 times a
second), the computer measures and saves the strength of the electrical
signal from the microphone, on a scale from 0 to 65,535.
That's it. Digital audio data is just a long series of numbers. The
computer sends these numbers, in the form of electrical signals, to a
speaker. The speaker then vibrates and generates the same sound that
was recorded.
The primary advantage of digital audio is the quality of the sound.
Unlike MIDI, a digital audio recording is very rich, capturing all the
nuances, overtones, and other characteristics of the sound exactly as
performed. The main drawback of digital audio is that it takes up a lot of
disk space. To record a 1-minute segment of stereo, CD-quality digital
audio, you need about 10 megabytes of disk space.
On the PC, digital audio is usually stored in wave Þles (extension .
WAV).
There are many programs available that let you create, play, and edit
these Þles. Pro Audio reads, writes, and lets you edit wave Þles.
More information about digital audio can be found in Chapter 7, Editing
Audio.
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