Reference Guide

58 Introduction
Computers, sound and music
Digital audio
Digital audio (frequently referred to here as just “audio”) is a simple way to record and play sounds of
any type. It works like a tape recorder—you record something, then later play it back. Digital audio
stores the sound as a long series of numbers. To record audio in SONAR, you have to have an audio
cable connecting the audio output of your electronic instrument to the audio input on your sound
card or audio hardware. If you’re recording vocals or an acoustic instrument, you need to connect a
microphone to the audio input on your sound card or audio hardware.
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 computer, digital audio is usually stored in Wave files (extension .wav). There are
many programs available that let you create, play, and edit these files. SONAR reads, writes, and
lets you edit Wave files.
Next topic: “Setup” on page 59