Apple Soundtrack Pro - Manual (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
Time