Glossary of Terms:
44.1 KHz: 44,100 cycles per second; A CD-player reads 44,100 samples (16-bits each) every second for each channel (typically stereo, left and right). This means that a standard stereo CD-player reads nearly one-and-a-half million zeros and ones every second.
48 KHz: 48,000 cycles per second; this is a slightly higher sampling rate than CD quality and is referred to as DAT quality.
60-Hz Hum: The low buzzing sound associated with AC power in the United States. Standard power generators in the U.S. turn at 1800rpm, causing the electrical current to change direction at double that frequency (1800rpm / 60sec * 2). A 60-Hz Hum will sound a little lower than a B-flat, but a little higher than a low A (55Hz).
96 KHz: 96,000 cycles per second; in audio, this is a significantly high sampling rate.
amplitude: the maximum displacement of a wave from resting state; in sound, this is perceived as volume or loudness.
attenuation: reduction of volume/amplitude.
aural exciter: adds shaped noise to an input signal to artificially add harmonics to the existing sound; This is useful for livening up a "dead" recording, or adding crispness or brightness to something that sounds too dark.
bandpass filter: A frequency-sensitive filter that only allows a particular band of frequencies to pass through, attenuating all other frequencies.
beats: A phenomenon that occurs when two simultaneous tones are slightly out of tune with each other; the difference in frequency will be perceived as a pulsation in the sound (beats) as the two tones alternately reinforce and disrupt each other.
bipolar: a microphone pattern that picks up primarily directly in front and behind the microphone; Also called a "figure 8" pattern.
bit-depth: Refers to the number of bits (ones and zeros) that make up each sample; the greater the bit depth, the richer and more realistic the sound will be; 8-bit sound is comparable to the audio quality of a telephone conversation, 16-bit sound is CD-quality, 24-bit sound is considered very high quality but is rare in consumer audio devices.
blue-book standard: specifications outlined in a document developed by Sony and Phillips in 1995 for "stamped multisession", or enhanced CDs.
bounce: to take several tracks of audio and mix them down to another track; this process was very common in the days when reel-to-reel recorders were limited to 16 tracks or less.
cardioid: A microphone pick-up pattern that is heart-shaped.
channel: A separate path for audio information to follow for processing; Stereo is 2 channels; Surround Sound typically has between 5 and 7 channels; some studios and sound reinforcement systems have mixing boards capable of handling 64 or more channels.
CD quality: The standard bit- and sampling-rate heard on a Compact Disc; 44,100 samples per second times 2 channels (left and right), 16 bits per sample
compression: Process by which the dynamic contrast of a signal is decreased. This makes the "louds" less loud and the "softs" less soft; very useful for evening out a source that goes extremes too much (such as the voice, or a drum) or to lend consistency to an instrument that is different volumes at different parts of its range (such as a bass guitar)
compander: A device or process that compresses and expands a signal, usually to eliminate background noise (especially on an analog tape).
constructive interference: Interference of two signals that causes them to amplify each other.
copyright: The right to publish, record, and/or perform a particular work.
DAT quality: 48KHz, 24-bits, stereo; slightly better than CD quality; typical of Digital Audio Tape (DAT).
de-esser: A compressor that only operates in a particular bandwidth (fairly high), so as to squash down excessively sharp-sounding S, F, T, and other sibilant consonant sounds.
delay: the process of splitting a signal in two and waiting for the first to begin sounding before allowing the second one to begin
destructive editing: editing which permanently alters the source file from which you are working
destructive interference: the effect of one wave pulling as another is pushing in the same place, fully or partially canceling each other's effort and minimizing the disturbance in the medium they're passing through at that point
Dolby 5.1: a proprietary system of producing six spatially located channels of audio (left front, center, right front, left rear, right rear, low frequency effects)
DSP: digital signal processing
DVD-Audio: a method of encoding high-resolution audio on a DVD, allowing for greater bit-depth and sampling rates than can be achieved on a standard audio CD.
dynamics processing: the use of an interactive process to control the volume output level of a channel; includes compression, expansion, limiting, and gating.
echo: a delayed repetition of a sound, occurring naturally when sound reflects of a hard, usually flat, surface
editing: in recording, the process of moving, cutting, and copying segments of recorded sound
envelope: a tool by which an effect or process can be varied over time, such as a volume graph
EQ: equalization; the process of increasing or decreasing particular ranges of frequencies in the audio spectrum to achieve a desired tonal balance
equal temperament: a tuning system by which only octaves are perfectly in tune, but all other intervals are compromised in their tuning so as to make all twelve tonal centers equally pleasing to the ear; this is the standard tuning system of modern Western music
expansion: process of making the louds louder and the softs softer
frequency: the rate at which something happens; in sound, frequency refers to the number of vibrations happen in a given amount of time and is measured in cycles per second, or Hertz; frequency is generally perceived as highness or lowness of pitch
fundamental: the lowest frequency at which a vibrating mass will resonate
gating: setting a minimum allowable sound level, thus eliminating low-level background sounds
glass mastering: the standard method of manufacturing commercial CDs; glass-mastered CDs store their data as a series of microscopic pits and bumps, as opposed to light and dark spots on a special photosensitive dye which comprise the encoding on a "burned" CD
graphic EQ: a form of equalization in which the audio spectrum is divided into discrete bands which are controlled by different sliders
harmonics: integer multiples of a fundamental frequency; for instance, if a fundamental tone is at 100Hz, its harmonics sound at 200Hz, 300Hz, 400Hz, etc.
hiss-reduction: practice of reducing unwanted high-end noise
Huygen's Principle: phenomenon in wave mechanics where higher frequencies are more directional than lower frequencies, which are better able to move around an obstruction
ISO 9002-compliant: ISO 9002 refers to a fairly recent set of quality management standards published by the International Organization for Standards, which was founded in Switzerland in 1947. Although obsolete in the face of the more recent ISO 9000:2000 standard, many CD manufacturers use the still-useful ISO 9002 specifications as their yardstick of quality control.
jitter: a type of audio signal distortion caused by transmission error in the time code
limiting: compression with a ratio of greater than 10:1, used to prevent audio from peaking
mastering: typically, preparing a finished mix for listening on consumer audio devices; this may involve multi-band compression, EQ, saturation, hard limiting, stereo spreading, trimming, normalization, and CD tracking/authoring.
mechanical licensing: permission to record and distribute a song that belongs to a living copyright owner (be it a person, estate, or publisher); i.e. - permission to record a song that is not in the public domain.
mixing: the process of adjusting the relative volume levels, panning, and effects of a multitrack recording.
modulation: in electronic sound, a wave whose amplitude or frequency are varied according to the shape of another wave.
mono: monophonic, having only one sound channel
MP3: Motion Picture Expert Group Layer 3, a "lossy" method of audio compression developed by gurus of the film industry for saving sound as a file 1/10th its uncompressed size
multiband compression: use of independent compressors for various ranges of the audio spectrum; especially useful in mastering
multichannel: having many channels of audio; in recording, this is significant in recording various instruments to separate tracks simultaneously
multitracking: saving audio (and video) to separate tracks which can be manipulated individually and yet played simultaneously
noise: random sound, typically containing all possible frequencies simultaneously
noise floor: the low-level bed of noise beneath the level of recording
noise reduction: one of several techniques for reducing or eliminating noise in a recording; one common way in digital audio is to take a sample of the noise by itself, then run a noise filter that analyzes that data and tries to extract those sounds from the recording
non-destructive editing: editing which does not alter the original sound file from which one is working
notch filter: an EQ filter that completely eliminates a specific narrow band of frequencies; useful for getting rid of 60-Hz hum and high-pitched synch signals from video equipment
octave: in sound, the perceived distance from one frequency to its exact double, e.g. 220Hz - 440Hz = an octave; in music, this corresponds to the difference in pitch of one note to the next highest (or lowest) note of the same name, e.g. A3-A4 = an octave.
omnidirectional: a microphone pick-up pattern that takes in sound equally from all directions
overdubbing: the process of recording a new audio track alongside a previously recorded track, usually for simultaneous playback later
overtone: another name for harmonic
overtone series: naturally occurring series of pitches that results from sounding each successive harmonic above a fundamental tone. Most of these overtones directly correspond to musical intervals
panning: moving an audio track right or left
parametric EQ: an EQ with adjustable controls for frequency and bandwidth, much more user-definable than a graphic EQ; very useful when it is "sweepable", meaning that the user can drag the frequency-selection across the audio spectrum to locate a trouble spot.
PCM: pulse code modulation; this is the method by which sound and video are converted into zeroes and ones.
phase: point in a waveform cycle, expressed in degrees; a wave passes through 360 degrees before it begins a new cycle
phase cancellation: phenomenon where two overlapping waves destructively interfere at a particular frequency and eliminate that frequency from each other at that point in space
pink noise: sound with all possible frequencies present at the same time, gradually rolling off toward the high end so that there are equal amounts of sound energy in each musical octave; sounds like a waterfall
phonorecord: an antiquated term that generally refers to any sound recorded in fixed form; used as a copyright term for Edison cylinders, vinyl records, 8-tracks, cassettes, CDs, DVD audio, etc.
pitch-correction: digitally tracking pitch in a recording of a solo instrument or voice and automatically adjusting it to adhere to a particular tuning and without changing its tempo.
Pythagorean tuning: a mathematically "perfect" tuning system in which a fifth is tuned to have a vibratory ratio of 3:2 and the fourth to a ratio of 4:3, leaving intervals such as major and minor thirds to be relatively complex (81:64, 32:27) and not quite as consonant; once one strays from the native key to which the instrument was tuned, the same musical intervals become very discordant.
Q: a number that describes how narrowly resonant a filter is in a parametric EQ; the higher the Q, the smaller the band of frequencies the filter will control.
red-book standard: specifications in a document authored by Sony and Phillips in 1980 for encoding a CD
reverb: "concert hall" effect caused by many echoes spaced so closely together that they are not individually distinguishable; this phenomenon is considered to be the primary component of a room's sound
shelving EQ: EQ that can be used to drag one end of the audio spectrum up or down
sine wave: a wave exhibiting simple harmonic motion; essentially a smooth, featureless wave
SMPTE: Society of Motion Picture and Television Engineers; often refers to SMTPE Time Code, a synchronization standard developed by the afore mentioned organization
sound shadow: much like a regular shadow, a sound shadow is an area where highly directional sound (high frequency) is obstructed by something, leaving an acoustical "shadow" behind it
stereo: stereophony; the now-standard practice of recording and reproducing audio in left and right channels so as to recreate the spatial nuances we naturally pick up on by having two ears spaced apart a certain distance.
surround sound: a method of recording and reproducing audio in 4 or more spatially located channels so as to create an immersive listening experience, particularly for film and television (see Dolby 5.1)
tempo: a musical term referring to the absolute speed at which a selection is played
unidirectional: a microphone pick-up pattern that selectively takes in sound only in one direction
vocal formants: natural resonances in the human vocal tract that add coloration to the sound of the voice and whose frequencies stay relatively constant, independent of the vocal folds; vocal formants sound in different proportions depending on the vowel sound being made, and their frequency can be slightly changed by the position of the jaw, tongue, and lips.
WAV: the standard format for uncompressed audio on Windows-based PCs
wave: a natural disturbance in a medium that moves out from its source, carrying energy with it
white noise: sound that has all possible frequencies present at the same time and at equal intensities; sounds like TV "static".
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