Reference
Audio Engineering Glossary
Clear definitions of 75 terms used in mixing, mastering and digital audio. Each entry links to the guide where the concept is explained in practice.
A
- AAX
- Avid Audio eXtension, the plugin format used by Pro Tools. Essential Plugins guide →
- Attack
- How quickly a compressor or limiter reacts once the signal exceeds the threshold, usually given in milliseconds. A slow attack lets transients through; a fast attack controls them. Compression guide →
- Automation
- Recorded changes to a parameter over time, such as volume rides on a vocal or a delay send raised on a single word. Vocal Chain guide →
- Aux send
- A secondary output from a track that feeds an auxiliary (return) channel, typically used to share reverb and delay between many tracks. Reverb & Delay guide →
B
- Bit depth
- The number of bits used per sample. 16-bit offers about 96 dB of theoretical dynamic range and 24-bit about 144 dB; 32-bit float adds a huge range for processing headroom. Mastering Chain guide →
- Brickwall limiter
- A limiter with a very high ratio, fast attack and lookahead that keeps the signal from exceeding a set ceiling. True Peak & LUFS guide →
- Bus
- A channel that combines several signals, such as a drum bus or the master bus, so they can be processed together. Compression guide →
C
- Ceiling
- The maximum output level of a limiter, commonly set to −1.0 dBTP for streaming masters. True Peak & LUFS guide →
- Clipping
- Distortion caused when a signal exceeds the maximum level a system can handle. It can be accidental, or used deliberately with a clipper to shave transients. Mastering Chain guide →
- Comb filtering
- A series of regularly spaced notches in the frequency response caused by combining a signal with a slightly delayed copy of itself. Stereo & Phase guide →
- Compressor
- A dynamics processor that reduces the level of a signal above a threshold by a set ratio, narrowing its dynamic range. Compression guide →
- Correlation meter
- A meter showing how similar the left and right channels are, from +1 (identical) through 0 (unrelated) to −1 (opposite polarity). Stereo & Phase guide →
- Crossover
- The frequency at which a multiband processor splits the signal into separate bands. Mastering Chain guide →
D
- dBFS
- Decibels relative to full scale. 0 dBFS is the highest level a digital system can represent. Gain Staging guide →
- dBTP
- Decibels true peak: the peak level including inter-sample peaks, estimated by oversampling. True Peak & LUFS guide →
- dBu
- An analog voltage level referenced to 0.775 V RMS. +4 dBu is professional line level. Gain Staging guide →
- De-esser
- A frequency-specific compressor that reduces sibilant sounds, usually between 5 and 8 kHz on vocals. Vocal Chain guide →
- Decay (RT60)
- The time a reverb takes to fall by 60 dB after the source stops. Reverb & Delay guide →
- Dither
- Low-level noise added when reducing bit depth, replacing truncation distortion with a smooth, benign noise floor. Mastering Chain guide →
- Dynamic EQ
- An equalizer band that only boosts or cuts when its frequency range crosses a threshold, combining EQ and compression. Parametric EQ guide →
- Dynamic range
- The difference between the loudest and quietest parts of a signal. Compression guide →
E
- Early reflections
- The first distinct echoes of a sound off nearby surfaces, which give the ear cues about room size and distance. Reverb & Delay guide →
- EBU R128
- A European broadcast loudness recommendation based on ITU-R BS.1770, with a target of −23 LUFS and a maximum of −1 dBTP. True Peak & LUFS guide →
F
- FET compressor
- A compressor that uses a field-effect transistor as its gain element, known for very fast attack and an energetic, aggressive character (1176 style). Compression guide →
- Floating point
- The number format DAWs use internally (32 or 64-bit). Its extremely wide range means internal levels above 0 dBFS don't clip permanently. Gain Staging guide →
- Fundamental
- The lowest frequency of a pitched sound, which defines the note we hear. Kick, Bass & 808 guide →
G
- Gain reduction
- The amount a compressor or limiter is lowering the signal at a given moment, shown in dB. Compression guide →
- Gain staging
- Managing signal levels at every point in the chain to stay clear of both noise and distortion. Gain Staging guide →
H
- Haas effect
- Also called the precedence effect: a delay of roughly 1–30 ms between two copies of a sound is heard as width or direction rather than as an echo. Stereo & Phase guide →
- Headroom
- The space between the current peak level and the maximum possible level, 0 dBFS. Gain Staging guide →
- High shelf
- An EQ band that raises or lowers all frequencies above a chosen point. Parametric EQ guide →
- High-pass filter
- A filter that removes frequencies below its cutoff, also called a low-cut. Its slope is given in dB per octave. Parametric EQ guide →
I
- Impulse response
- A recording of how a space or device responds to a short impulse, used by convolution reverbs to recreate that space. Reverb & Delay guide →
- Integrated loudness
- The average loudness of an entire track in LUFS, measured according to ITU-R BS.1770. True Peak & LUFS guide →
- Inter-sample peak
- A peak in the reconstructed analog waveform that occurs between digital samples and can exceed 0 dBFS. True Peak & LUFS guide →
K
- K-weighting
- The frequency weighting used for LUFS measurement. It reduces the influence of low frequencies and slightly emphasizes the upper range, roughly matching human hearing. True Peak & LUFS guide →
- Knee
- How gradually a compressor moves from no compression to its full ratio around the threshold. Compression guide →
L
- Latency
- The delay introduced by audio buffers or plugin processing, measured in samples or milliseconds. Essential Plugins guide →
- LCR panning
- A mixing approach that places every element hard left, center or hard right. Stereo & Phase guide →
- Limiter
- A compressor with a very high ratio, used to stop peaks from exceeding a set level and to raise overall loudness. True Peak & LUFS guide →
- Linear phase EQ
- An EQ that delays all frequencies equally, preserving phase relationships at the cost of latency and possible pre-ringing. Parametric EQ guide →
- Lookahead
- A short internal delay that lets a limiter or compressor react to peaks before they arrive. True Peak & LUFS guide →
- Loudness normalization
- Automatic playback level adjustment by streaming services so that tracks play at similar loudness. True Peak & LUFS guide →
- Loudness range (LRA)
- A measure of how much the loudness varies across a track, expressed in LU. True Peak & LUFS guide →
- LUFS
- Loudness Units relative to Full Scale, the standard unit of perceived loudness. 1 LU equals 1 dB. True Peak & LUFS guide →
M
- Makeup gain
- Gain added after compression to restore the overall level. Compression guide →
- Mid/side (M/S)
- A way of representing stereo as the sum (mid) and difference (side) of left and right, allowing the center and the width to be processed separately. Stereo & Phase guide →
- Minimum phase
- The normal behavior of analog and most digital EQs, where changes in level are accompanied by phase shifts around the affected band. Parametric EQ guide →
- Mono compatibility
- How well a stereo mix holds up when the left and right channels are summed to mono. Stereo & Phase guide →
- Multiband compression
- Compression applied separately to several frequency bands that are split by crossovers. Mastering Chain guide →
O
- Opto compressor
- A compressor that uses a light source and photocell, known for smooth, program-dependent behavior (LA-2A style). Compression guide →
- Oversampling
- Processing audio internally at a multiple of the sample rate to reduce aliasing or to detect true peaks more accurately. True Peak & LUFS guide →
P
- Parallel compression
- Blending a heavily compressed copy of a signal with the uncompressed original, also known as New York compression. Compression guide →
- Phase
- The position in time within a waveform's cycle. Combining signals that are out of phase causes cancellation. Kick, Bass & 808 guide →
- Polarity
- Whether a waveform is upright or inverted. Flipping polarity inverts the signal instantly; it isn't the same as a time delay. Kick, Bass & 808 guide →
- Pre-delay
- The time between the direct sound and the start of the reverb. Reverb & Delay guide →
- Pre-ringing
- Energy that appears just before a transient, caused by the symmetric impulse response of linear phase filters. Parametric EQ guide →
- Proximity effect
- The bass boost directional microphones produce when the source is very close to the capsule. Vocal Chain guide →
Q
- Q factor
- A measure of EQ bandwidth: center frequency divided by bandwidth in Hz. A higher Q means a narrower band. Parametric EQ guide →
R
- Ratio
- How strongly a compressor reduces the signal above the threshold. At 4:1, a signal 4 dB over the threshold comes out 1 dB over. Compression guide →
- Reference track
- A commercial recording used for comparison while mixing or mastering, always played at matched loudness. Mastering Chain guide →
- Release
- How quickly a compressor or limiter returns to no gain reduction after the signal falls below the threshold. Compression guide →
- Room mode
- A standing wave between room surfaces that causes strong peaks and dips at specific low frequencies. Acoustics & Monitoring guide →
S
- Sample rate
- The number of samples per second, such as 44.1 kHz or 48 kHz. The highest frequency that can be represented is half the sample rate. Mastering Chain guide →
- Saturation
- Gentle harmonic distortion that adds warmth and density and helps sounds stay audible on small speakers. Kick, Bass & 808 guide →
- Sibilance
- Harsh “s”, “sh” and “t” sounds in vocals, usually concentrated between 5 and 8 kHz. Vocal Chain guide →
- Sidechain
- An input that lets one signal control a processor acting on another, for example a kick ducking a bass. Kick, Bass & 808 guide →
- Slapback
- A single short echo, typically 60–120 ms, used to thicken vocals and guitars. Reverb & Delay guide →
- Stem
- A submix of a group of tracks, such as drums, vocals or bass, exported as one audio file. Finishing AI Songs guide →
T
- Threshold
- The level above which a compressor, limiter or gate starts to act. Compression guide →
- Transient
- The short, high-energy start of a sound, such as the crack of a snare. Compression guide →
V
- Vari-Mu compressor
- A tube compressor in which the ratio rises as the input gets louder, known for smooth, warm glue. Compression guide →
- VCA compressor
- A compressor that uses a voltage-controlled amplifier, known for clean, fast and precise control. Compression guide →
- VST3
- The current version of Steinberg's Virtual Studio Technology plugin format, widely supported on Windows and macOS. Essential Plugins guide →
- VU meter
- An averaging level meter with roughly 300 ms integration time, showing perceived level more than peaks. Gain Staging guide →