SOUNDBOOTH CS3
User Guide
82
Nyquist frequency
A frequency equal to half the current sample rate, which determines the highest reproducible
audio frequency for that rate. For example, audio CDs use a sample rate of 44,100 Hz because the resulting Nyquist
frequency is 22,050 Hz—just above the limit of human hearing, 20,000 Hz. For the best audio quality, record and edit
at higher sample rates and then convert down if needed.
O
offline processing
Intensive effects processing that requires dedicated computer power, briefly preventing you from
editing audio. (Compare with “real time” on page 82.)
P
PCM
(pulse code modulation) PCM is the standard method used to digitally encode audio and is the basic, uncom-
pressed data format used in file formats such as WAV and AIFF.
phase
The position of a sound wave relative to other sound waves. As a sound wave travels through the air, it
compresses and expands air molecules in peaks and troughs, much like an ocean wave. In the Soundbooth waveform
display, peaks appear above the center line, troughs appear below. If two channels of a stereo waveform are exactly
opposite in phase, they will cancel each other out. More common, however, are slightly out-of-phase waves, which
have misaligned peaks and troughs, resulting in duller sound. (See also “Waveform measurements” on page 12.)
Q
quantization
A process that occurs when an analog waveform is converted to digital data and becomes a series of
samples. Quantization noise is introduced as some samples are shifted to quantization levels allowed by the current
bit depth. This noise is highest at low bit depths, where it can particularly affect low-amplitude sounds.
R
RCA cable
Sometimes called a phono cable, RCA cables have RCA plugs or jacks at either end and are normally used
to connect stereo system components, such as receivers, CD players, and cassette decks.
real time
In computer-based audio, real time refers to functions that immediately respond to user input. Note,
however, that system speed ultimately determines processing time. (Compare with “offline processing” on page 82.)
resample
To convert a sound file to a different sample rate and bit depth.
reverb
The reverberant sound produced by an acoustic space, such as a room or concert hall. Reverb consists of
dense, discrete echoes that arrive at the ear so rapidly that the ear can’t separate them.
RMS
(Root-mean-square) A mathematical formula used to determine the average amplitude of an audio selection.
RMS amplitude reflects perceived loudness better than peak amplitude.
S
sample
A digital snapshot of an audio waveform at a particular point in time. In digital audio, a series of numeric
samples reproduces an entire waveform, with higher sample rates producing increased frequency response. (Note
that musical samplers use the term
sample
to describe a digital recording, rather than a digital snapshot.)
sample rate
The number of samples per second. Higher sample rates produce increased frequency response but
require more disk space. To reproduce a given audio frequency, the sample rate must be at least double that
frequency. (See “Nyquist frequency” on page 82.)
signal-to-noise ratio
Describes the difference between the highest signal level before distortion and the average level
of the noise floor. In most analog systems, such as microphone preamps, the signal-to-noise ratio is around 92 dB.
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