Audio Engineering Glossary
111 terms · from fundamentals to synthesis
Quick-reference definitions for every term used across the TeachMe curriculum. Hover over highlighted terms in any lesson to see a preview, or browse the full glossary here.
A
Absorption
The conversion of sound energy into heat by a material. Soft, porous materials (foam, fiberglass, mineral wool) absorb high frequencies well; dense thick panels are needed for low frequencies.
Acoustic Treatment
Materials and structures placed in a room to control reflections, absorption, and diffusion. Includes absorption panels, bass traps, and diffusers — distinct from soundproofing.
Amplitude
The magnitude of a sound wave's pressure variation from its resting state. Greater amplitude means a louder sound.
Attack Time
How quickly a compressor or gate responds once the signal crosses the threshold. A fast attack (< 1 ms) clamps transients; a slow attack (50–100 ms) lets transients through for punch.
Audio Interface
Hardware that converts analog audio to digital and back (ADC/DAC), connecting microphones and instruments to a computer. Quality determines noise floor, latency, and headroom.
B
Bass Trap
An acoustic absorber designed to absorb low-frequency energy. Typically placed in room corners where bass buildup is worst. Must be physically thick (at least 4–6 inches) to be effective at low frequencies.
Bleed (Spill)
Unwanted sound from nearby sources leaking into a microphone not intended to capture it — e.g., hi-hat bleed into the snare mic. Controlled by mic placement, polar pattern choice, and gobos.
Bus (Subgroup)
A channel that receives signals from multiple tracks summed together. Drum buses, stem buses, and master buses allow group processing and level control.
C
Clipping
Distortion that occurs when a signal exceeds the maximum level a system can handle (0 dBFS digital; the power supply rail in analog). Digital hard clipping creates harsh square-wave distortion.
Comb Filtering
A series of regularly-spaced peaks and notches in the frequency response caused by two copies of a signal arriving at slightly different times. Looks like a comb on a spectrum analyzer. Can be caused by room reflections or phase issues when combining microphones.
Compression Ratio
The amount of gain reduction applied above the threshold. A 4:1 ratio means every 4 dB above threshold results in only 1 dB of output increase. A ratio of ∞:1 is a brick-wall limiter.
Compressor
A dynamics processor that reduces the level of signals above a set threshold by a defined ratio. Used to control dynamic range, add punch, and glue elements together.
D
dBFS (dB Full Scale)
A decibel scale where 0 dBFS represents the maximum digital level. All digital levels are negative (e.g., −18 dBFS is a common target for individual tracks). Exceeding 0 dBFS causes clipping.
De-Esser
A frequency-selective compressor or EQ targeting sibilance frequencies (typically 5–10 kHz). Reduces harsh "s," "sh," and "t" sounds in vocal recordings.
Delay
An effect that records a signal and plays it back after a set time. Types include tape delay (warm, self-oscillating), digital delay (precise), and multi-tap delay (multiple repeats at different times).
Diffusion
The scattering of sound in multiple directions, reducing specular (mirror-like) reflections while preserving a sense of spaciousness. QRD (quadratic residue diffuser) panels are a common type.
Dither
Low-level noise added to a digital audio signal before reducing bit depth to minimize quantization distortion. Always apply dither when bouncing a final master to 16-bit for CD.
Ducking
Using sidechain compression to automatically lower the level of one signal when another is present. Common in broadcast (voice lowers music) and EDM production (bass ducks to kick).
Dynamic Range
The difference between the quietest and loudest level a system can faithfully reproduce. 24-bit audio has ~144 dB of theoretical dynamic range, far exceeding the ~70 dB of typical listening environments.
E
Early Reflections
The first distinct reflections arriving at the listener within ~80 ms of the direct sound. Early reflections contribute to perceived room size and can cause comb filtering if untreated.
Envelope (ADSR)
A four-stage contour that shapes a parameter over time: Attack (rise time), Decay (fall to sustain level), Sustain (held level while note is held), Release (fade after note ends). Applied to amplitude, filter, or any modulatable parameter.
EQ (Equalizer)
A tool for boosting or cutting specific frequency ranges in a signal. Types include parametric (adjustable frequency, gain, Q), graphic (fixed bands), and shelving (affects all frequencies above/below a point).
F
Fader
A slider or virtual control that adjusts the output level of a channel after all processing. Unlike gain, fader moves don't affect plugin input levels. Unity gain = 0 dB, meaning no amplification or attenuation.
Frequency
The number of complete wave cycles per second, measured in Hertz (Hz). Frequency determines what we perceive as pitch — higher frequency equals higher pitch.
Fundamental Frequency
The lowest and usually strongest frequency in a complex sound, which our ears hear as the perceived pitch. All other components are harmonics above this base frequency.
G
Gain
The amplification or attenuation applied to a signal, measured in dB. Unlike a fader (which adjusts output level post-processing), a preamp gain control sets the input level before any processing.
Gain Reduction
The amount of attenuation (in dB) that a compressor, limiter, or expander is currently applying to the signal. Displayed in real-time on a GR meter.
Gain Staging
The practice of setting optimal signal levels at every stage of the signal chain to maintain adequate signal strength while avoiding clipping and excessive noise. Targets are typically −18 to −12 dBFS for individual tracks.
H
Harmonic
A frequency that is an integer multiple of a fundamental frequency. The 2nd harmonic is twice the fundamental, the 3rd is three times, and so on. Harmonics define the timbre of an instrument.
Headroom
The difference between the current peak signal level and 0 dBFS (the maximum). Sufficient headroom (typically 6–12 dB in mixing) prevents clipping and leaves room for dynamics and mastering processing.
High-Pass Filter (HPF)
A filter that allows frequencies above a set cutoff point to pass through while attenuating lower frequencies. Used to remove unwanted rumble, HVAC noise, and proximity-effect bass buildup.
I
Impedance
Electrical resistance to alternating current, measured in ohms (Ω). For optimal signal transfer, the output impedance of one device should be much lower than the input impedance of the next device in the chain (1:10 rule).
K
Knee (Hard / Soft)
How abruptly a compressor transitions from no compression to full compression at the threshold. A hard knee switches immediately; a soft knee gradually increases compression over a range centered on the threshold.
L
Latency
The delay between an audio input event and when you hear it through the system, caused by ADC conversion, buffer processing, and plugin computation. Buffer size controls the tradeoff: smaller buffers = lower latency but more CPU strain.
LFO (Low-Frequency Oscillator)
An oscillator running at sub-audio frequencies (0.01–20 Hz) used to modulate parameters like pitch (vibrato), volume (tremolo), or filter cutoff (wah). LFOs are not heard directly; they create movement and modulation.
Limiter
A compressor with a very high ratio (typically 10:1 or higher, or ∞:1) that prevents the signal from exceeding a set ceiling. Used to protect speakers and achieve loud masters.
Line Level
A standard signal level used by professional audio equipment, nominally +4 dBu in pro gear and −10 dBV in consumer gear. Line-level signals are strong enough to connect directly to mixers, interfaces, and amplifiers.
Loudness
The perceived intensity of a sound as experienced by a listener, which integrates level over time. Perceptual loudness is different from peak level; compressors and limiters are used to increase apparent loudness.
Low-Pass Filter (LPF)
A filter that allows frequencies below a set cutoff point to pass through while attenuating higher frequencies. Used to remove harshness, tame cymbals, or create effects.
LUFS (Loudness Unit Full Scale)
A loudness measurement standard (ITU-R BS.1770) that models how humans perceive loudness over time. Streaming platforms normalize tracks to targets like −14 LUFS (Spotify) or −16 LUFS (Apple Music).
M
M/S Processing
Mid-Side processing encodes a stereo signal into its center (Mid = L+R) and sides (Side = L−R) components for independent processing. Allows you to EQ only the stereo width or compress the center without affecting the sides.
Microphone
A transducer that converts acoustic pressure waves into electrical signals. Main types: dynamic (robust, handles high SPL), condenser (detailed, needs phantom power), and ribbon (warm, figure-8 pattern).
MIDI (Musical Instrument Digital Interface)
A communication protocol that transmits musical event data — note on/off, velocity, pitch bend, controller values — rather than audio. MIDI itself makes no sound; it controls instruments and plugins.
Mono Compatibility
How a stereo mix sounds when collapsed to a single mono channel. Phase cancellation can make wide stereo elements disappear or thin out in mono — critical for streaming, phone speakers, and club systems.
N
Noise Floor
The level of inherent noise in an audio system below which signals cannot be heard. Good microphone preamps have noise floors well below −100 dBu. Recording louder (higher gain staging) improves signal-to-noise ratio.
Notch Filter
A very narrow, high-Q cut used to eliminate a specific frequency — for example, removing a 60 Hz electrical hum or a harsh resonance. The opposite of a peak band.
O
Octave
An interval representing a doubling or halving of frequency. Middle C is 262 Hz; the C one octave above is 524 Hz. EQ bands are often described in octave widths.
Oscillator
The sound-generating component of a synthesizer that produces a periodic waveform (sine, sawtooth, square, triangle). Multiple oscillators are commonly detuned slightly against each other for a richer sound.
Overtone
Any frequency component above the fundamental in a complex sound. Overtones include harmonics (integer multiples) and inharmonic partials. The unique mix of overtones gives each instrument its characteristic sound.
P
Panning
The placement of an audio signal in the stereo field between left and right channels. Creates width and separation in a mix, helping instruments occupy their own space.
Parallel Compression
A technique where a heavily compressed copy of a signal is blended with the uncompressed original. Retains the transient punch of the dry signal while adding the density and sustain of compression.
Parametric EQ
An equalizer with adjustable frequency, gain (dB boost or cut), and bandwidth (Q) for each band. The most flexible and common type used in professional mixing.
Phantom Power (+48V)
A DC voltage (48V) supplied through an XLR cable to power condenser microphone capsules. Required by most condenser mics; generally safe to use with dynamic mics but can damage some ribbons.
Phase
The position of a wave in its cycle, measured in degrees (0°–360°). When two signals are 180° out of phase, they cancel each other — this is called destructive interference.
Phase Cancellation
The reduction in amplitude that occurs when two signals with similar content are combined but are out of phase with each other. Can cause thin sound, hollow bass, or complete signal dropout.
Pitch
The perceived highness or lowness of a sound, directly correlated with frequency. Concert A is 440 Hz; octaves double or halve this value.
Pitch Correction
Processing that shifts the pitch of audio to target notes. Subtle use (e.g., Auto-Tune with slow retune speed) is transparent; aggressive use creates the T-Pain/Kanye "robotic" effect.
Polar Pattern
The directional sensitivity of a microphone. Key patterns: cardioid (front-focused), omnidirectional (all directions), and figure-8 (front and back). Pattern affects bleed, room sound, and proximity effect.
Polarity (Phase Flip)
Inverting the polarity of a signal flips the positive and negative halves of the waveform (a 180° shift). Often mislabeled "phase" on mixers. Used to fix phase cancellation when combining multiple microphones.
Pre-Delay
A short delay (typically 10–30 ms) before the reverb tail begins. Pre-delay separates the dry sound from the reverb wash, maintaining the clarity and up-front feel of the original signal.
Preamp (Preamplifier)
An amplifier that boosts a microphone-level or instrument-level signal up to line level, where it can be recorded or processed. Preamp character (clean vs. colored) significantly affects tone.
Proximity Effect
The increase in low-frequency response of directional microphones as the sound source moves closer. At 1–2 cm, bass can be boosted by 10–16 dB, which can be used creatively or corrected with high-pass filtering.
Pumping
An audible artifact where the gain of a compressor rapidly rises and falls, causing a rhythmic "breathing" effect. Can be intentional (e.g., sidechain compression in EDM) or a problem to avoid.
Q
Q Factor
The bandwidth of an EQ band: Q = center frequency ÷ bandwidth. A high Q (e.g. 10) creates a very narrow, surgical cut; a low Q (e.g. 0.5) creates a broad, gentle curve. Also called resonance in some filter contexts.
R
Release Time
How quickly a compressor stops applying gain reduction after the signal falls below the threshold. Too short a release causes distortion (pumping); too long can sound unnatural.
Reverb
An effect that simulates the acoustic reflections of a space. Types include room, hall, plate, spring, and convolution reverb. Characterized by pre-delay, decay time, and diffusion.
Reverberation (Reverb)
The persistence of sound in a space after the source stops, caused by many reflections arriving so closely spaced that the ear perceives them as a continuous decay. Characterized by RT60 — the time for sound to decay 60 dB.
Room Modes
Standing waves that build up in a room when the wavelength of a sound matches or is a fraction of a room dimension. Room modes cause bass frequencies to be unevenly loud or quiet at different positions.
RT60
The reverberation time — how long (in seconds) it takes for sound in a room to decay by 60 dB after the source stops. A studio control room typically targets 0.2–0.4 s.
S
Saturation
Soft, gradual harmonic distortion modeled after analog tape or tube gear, adding warmth and "glue" without harshness. Different from digital clipping, which is abrupt and harsh.
Sends & Returns (Aux)
A routing system where individual tracks send a portion of their signal to a shared effects bus (return channel). Allows many tracks to share a single reverb or delay instance, saving CPU and ensuring cohesion.
Shelving EQ
An EQ band that applies a uniform boost or cut to all frequencies above (high shelf) or below (low shelf) a transition frequency. Used for tonal balance — "air" boosts at 12 kHz or low-end warmth at 100 Hz.
Sibilance
Harsh high-frequency energy in the 5–10 kHz range, created by "s," "sh," "ch," and "t" sounds in vocals. Microphone proximity and certain condenser mics can exaggerate sibilance.
Sidechain
A secondary input signal used to control the behavior of a dynamics processor. For example, routing a kick drum into the sidechain of a bass compressor so the bass ducks every time the kick hits.
Signal Chain
The sequence of hardware or software components a signal passes through from source to destination. Order matters: placing EQ before compression gives different results than the reverse.
Signal Routing
How audio signals are directed between inputs, tracks, buses, effects, and outputs within a DAW or mixing console. Good routing keeps the signal chain logical and prevents unwanted feedback loops.
Standing Wave
A wave pattern where two identical waves traveling in opposite directions combine to create fixed points of maximum and minimum amplitude. In rooms, standing waves cause bass buildup and nulls.
Stereo Width
The perceived spread of a sound between the left and right channels. Artificially widening with M/S processing or chorus can make a mix sound more expansive but risks mono-compatibility issues.
Streaming Normalization
Automatic gain adjustment applied by streaming platforms (Spotify, Apple Music, YouTube) to match tracks to a target loudness. Overly loud masters are turned down, so crushing dynamics for loudness is counterproductive.
Subtractive Synthesis
The most common synthesis method: start with a harmonically rich waveform (sawtooth or square) and subtract frequencies using a filter to sculpt the desired sound.
T
Threshold
The level (in dB) above which a compressor, limiter, or gate begins to act. Signals below the threshold pass through unaffected; signals above are processed.
Timbre
The tonal quality or "color" of a sound that distinguishes it from other sounds at the same pitch and loudness. Determined by the relative amplitudes of harmonics and overtones.
Transient
A short-duration, high-amplitude spike at the start of a sound — like the attack of a snare or the pluck of a guitar string. Transients define the "punch" and "snap" of a mix.
Tuning
The adjustment of an instrument or voice to a specific pitch standard. Concert pitch = A440 Hz. Proper tuning before recording prevents intonation problems that are difficult to fix in post.
V
Vibrato
A periodic pitch fluctuation applied to a sustained note, typically produced by an LFO modulating pitch. Common in vocals and string instruments for expressiveness.
Vocal Chain
The sequence of processing applied to a vocal track — typically: HPF → EQ → compression → de-esser → reverb/delay. Order matters for achieving clarity, body, and presence.
W
Waveform
The shape of a sound wave when plotted as amplitude over time. Common synthesizer waveforms: sine (pure, no harmonics), sawtooth (all harmonics, bright and buzzy), square (odd harmonics, hollow), triangle (odd harmonics, softer than square).
Wavelength
The physical distance between two consecutive peaks of a sound wave. Wavelength equals the speed of sound divided by frequency (λ = c / f). Low-frequency waves are physically large, which is why bass traps must be thick.
Wet / Dry Mix
The blend between the processed (wet) signal and the original unprocessed (dry) signal. 100% wet = only the effect; 100% dry = no effect. Also called mix knob on many plugins.