Apple Soundtrack Pro User Manual download pdf (Page 290)

290 Appendix C Audio Basics

Analog Recording

When a sound is recorded using analog technology, the sound waves are recorded as a

continuous electrical signal. Typically, the vibrations in the air contact the diaphragm of

a microphone, setting the diaphragm in motion. A transducer in the microphone

converts the diaphragm’s motion into an electric signal. The compressed parts of the

sound wave are recorded as positive electrical voltages, and the rarefied parts of the

wave are recorded as negative voltages. The voltage of the recorded signal is an analog

of the wave’s frequencies and their relative amplitudes at any point in time.

Analog recording technology was originally developed using mechanical means to

etch the sound signal directly onto wax cylinders or lacquer disks. Its simplicity, and the

rapid development of electronics during the twentieth century, led to its widespread

use for recording music and for adding sound to motion pictures.

However, analog audio recording is subject to several problems in achieving high-

fidelity reproduction of sound. These include noise, distortion, and loss of quality each

time the audio signal is copied or reproduced.

Digital Recording

When a sound is digitally recorded, the sound waves are recorded as a series of samples

onto a hard disk or other digital storage medium. A sample stores the voltages

corresponding to the wave’s frequencies and their relative amplitudes as a series of

binary numbers, or bits. Each sample is like a snapshot of the sound at a particular

instant in time.

Time

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Apple Soundtrack Pro User Manual Page 290