Dictionary

The technical words used across our products. Each term has its scientific definition, what it means in plain words, and how it is used in a real session.

79 terms

A

Acoustic calibrator

Also: calibrator, sound calibrator

Definition: A device that produces a known sound pressure level, typically 94 dB (1 Pa) or 114 dB at 1 kHz, in a coupler that fits over a measurement microphone (IEC 60942).
In plain words: A small device you put over the microphone that plays a tone at a known, stated level.
In use: Calibrate the measurement chain on it once the rig is set up, so levels read in dB SPL. This sets level at one frequency; it does not correct the microphone's frequency response (that is the correction file). Check again after changing gain, interface, input or other settings in the chain.

AcoustiTrack

%ALcons

Also: ALcons, articulation loss of consonants

Definition: Articulation Loss of Consonants: an empirical estimate, after Peutz, of the percentage of consonants a listener is likely to mishear. It is commonly converted from the STI; lower is better.
In plain words: The share of consonants people are likely to miss. Five percent or less is very good; above about fifteen percent speech becomes hard to follow.
In use: An older intelligibility scale still found in loudspeaker design and system specifications. Read it alongside STI when a client or a specification states its target in %ALcons.

AcoustiTrack

Audio Unit

Also: AU, Audio Units, AU plug-in

Definition: Apple's plug-in format for audio effects and instruments on macOS, loaded by Logic Pro and other Mac audio applications.
In plain words: The kind of plug-in Logic Pro uses: an effect or an instrument that loads into a channel.
In use: Logic Pro loads Audio Unit plug-ins, so a tool that works inside Logic arrives as an AU. TrackSpace's probe is an Audio Unit that you insert last on each channel, and it passes the audio through untouched.

TrackSpace

Aux channel

Also: aux, auxiliary channel, aux track, aux channel strip

Definition: A mixer channel strip with no audio region of its own; it takes its input from a bus or another source, such as an extra output of a software instrument, processes and levels that signal and passes it to its output.
In plain words: A mixer channel that plays no recording itself — it takes what is routed to it, often a bus, so you can treat a group of tracks or an effect as one fader.
In use: Auxes carry reverb and delay returns, drum and vocal groups, and parallel compression. An aux whose output goes nowhere, or that nothing feeds, is a common leftover from earlier mix revisions — it costs nothing to hear but changes what the mix actually contains.

SessionMap

B

Bus

Also: buss, busses, buses, aux bus

Definition: A shared signal path that combines the signals sent or routed to it and makes them available to the channel strips or processors that take it as an input — usually an aux channel strip.
In plain words: A shared line that several tracks can feed at once, so they can be processed or levelled together.
In use: Busses group tracks (all drums to one bus), share an effect (every vocal sent to one reverb) or feed a sidechain. In Logic Pro they are numbered — Bus 1, Bus 2 — and are usually picked up by an aux. SessionMap flags a bus that nothing arrives at.

SessionMap

C

C50

Also: clarity 50, speech clarity

Definition: Clarity index for speech: ten times the base-10 logarithm of the ratio of the energy arriving in the first 50 ms after the direct sound to the energy arriving after 50 ms, in dB (ISO 3382-1).
In plain words: How much of a sound arrives early enough to help the ear make out words, compared with what arrives later and smears them. Higher is clearer.
In use: A figure for speech rooms: lecture halls, conference rooms, houses of worship, spoken-word stages. A positive value means more early than late energy, which favours clear speech, but it is not a complete intelligibility test — noise and level matter too. Measure it at the seats where people complain, before and after a change.

AcoustiTrack

C80

Also: clarity 80, music clarity

Definition: Clarity index for music: ten times the base-10 logarithm of the ratio of the energy arriving in the first 80 ms after the direct sound to the energy arriving after 80 ms, in dB (ISO 3382-1).
In plain words: The balance between the sound that makes music sound defined and the reverberation that makes it sound full. Higher is more defined, lower is more blended.
In use: A figure for music rooms. Suitable values depend on the music and the room — values around 0 dB are often cited for orchestral halls, and amplified venues and studios often aim higher. Use it to compare seats, or a hall empty and full, under the same measurement conditions.

AcoustiTrack

Centre time

Also: Ts, center time, centre of gravity time

Definition: The time of the centre of gravity of the squared impulse response, in milliseconds, measured from the direct sound (ISO 3382-1).
In plain words: The moment at which, on average, the sound energy reaching a seat has arrived. Earlier means clearer; later means more reverberant.
In use: A clarity measure with no fixed 50 or 80 ms boundary, so it changes smoothly rather than jumping when a reflection moves across a boundary. Useful for comparing seats or treatment options with a single number.

AcoustiTrack

Channel strip

Also: channel strips, mixer channel

Definition: One column of a mixer: the input, inserts, sends, pan, fader and output assignment that process and route a single track, aux or output.
In plain words: One channel's column in the mixer, with everything that shapes and routes its sound.
In use: A channel strip shows its own settings but not where its signal goes after it leaves; working out a session's routing in the mixer means opening strips one at a time. SessionMap shows the connections between them instead.

SessionMap

Coherence

Also: magnitude-squared coherence, γ²

Definition: The magnitude-squared coherence γ²(f) = |Gxy|² / (Gxx · Gyy), between 0 and 1: the fraction of the measured output power at each frequency that is linearly explained by the reference input.
In plain words: An indicator, per frequency, of how consistently the microphone signal is linearly related to the reference. High values support the transfer-function reading; they do not prove the microphone is calibrated or that only the intended sound path was measured.
In use: Read the transfer function where coherence is high. Low coherence can come from noise, too little test signal at that frequency, a response that changes during the measurement, distortion or the measurement settings. Steady reflections are part of the linear response and need not lower it. Coherence needs averaging to mean anything.

AcoustiTrack

Complex averaging

Also: vector averaging, vector average, polar averaging, Polar (complex)

Definition: Averaging successive measurements of a complex quantity, such as a transfer function, by averaging their real and imaginary parts and then taking magnitude and phase from the result. Components with a stable phase relationship to the reference are kept; components whose phase varies, such as uncorrelated noise, partly cancel. Not the same as polar (magnitude-only) averaging in other analysers, nor as a power or decibel mean.
In plain words: An average that includes timing as well as level, so random noise tends to cancel while the system's steady response remains.
In use: Use it while the response and the timing reference stay stable — it suppresses noise in a busy room. If the response itself moves, for example outdoors in wind or with people walking past the microphone, it also cancels part of the real signal; switch to RMS (power) magnitude averaging. In AcoustiTrack the transfer function's "Polar (complex)" setting is this complex average; the RMS setting averages magnitude as power while phase and coherence stay complex.

AcoustiTrack

Control surface

Also: control surfaces, hardware control surface

Definition: A hardware controller with faders, knobs and buttons that operates a DAW's mixer remotely over a control protocol such as Mackie Control, and receives the mixer's current settings in return.
In plain words: A desk of physical faders and knobs that drives the mixer in your recording software and shows what that mixer is doing.
In use: A control surface and the DAW keep each other up to date, so the DAW tells the surface where every fader and pan knob is. TrackSpace's Hub connects to Logic Pro the way a control surface does, which is how it reads the real pan positions.

TrackSpace

Correlation meter

Also: phase correlation, phase correlation meter, correlation coefficient

Definition: A meter showing the normalised cross-correlation of the left and right channels at zero lag, from +1 (identical: mono) through 0 (unrelated) to −1 (identical but opposite in polarity).
In plain words: A meter that shows how well the left and right sides of a stereo track agree: towards +1 they add up when played in mono, towards −1 they cancel.
In use: Watch it for mono compatibility. A wide but healthy stereo track reads between 0 and +1; a reading that sits below zero means part of the track will lose level or disappear in mono, so listen to that track in mono before the mix ships. TrackScope shows one for every track in its Phase view.

TrackScope

Crest factor

Definition: The ratio of a signal's peak value to its RMS value, usually in dB.
In plain words: How far a signal's peaks rise above its average level.
In use: Sets how much headroom a test signal needs. A sine's crest factor is about 3.01 dB. Noise has no fixed ceiling: the peaks depend on how it is generated and how long you observe it, so check the generator's peak level rather than assuming one.

AcoustiTrack

D

D50

Also: definition, Deutlichkeit

Definition: Definition: the ratio of the energy arriving in the first 50 ms after the direct sound to the total energy of the impulse response, expressed as a fraction or a percentage (ISO 3382-1).
In plain words: The share of all the sound reaching a listener that arrives within the first 50 ms — the share that helps speech be understood.
In use: A speech measure that reads as a percentage; higher favours speech, but it is not a complete intelligibility test. It carries the same information as C50 on a different scale, so use whichever your client or specification asks for.

AcoustiTrack

dB SPL

Also: sound pressure level, SPL

Definition: Sound pressure level: Lp = 20 · log10(p / p0) dB, where p is the RMS sound pressure and p0 = 20 µPa, the reference pressure in air.
In plain words: The level of sound pressure in the room on the scale sound level meters and noise rules use. It is a measured level, not the loudness a listener perceives.
In use: With a calibrated measurement chain, levels read in dB SPL — the basis for level limits, noise exposure and comparing venues. State the frequency weighting, time weighting and bandwidth with the figure.

AcoustiTrack

dBFS

Also: decibels relative to full scale

Definition: Decibels relative to digital full scale: 0 dBFS is the full-scale reference of the converter or format, and levels below it are negative. Sample peaks are measured against it; floating-point signals can exceed it, and true-peak and RMS readings follow their own conventions.
In plain words: A level measured against the ceiling of the audio interface, not against the room.
In use: The scale for setting gain structure: keep test-signal peaks well below 0 dBFS so nothing clips, and keep the microphone signal well above the noise floor. A calibrated measurement chain turns input levels into dB SPL; it does not turn a transfer-function gain into SPL.

AcoustiTrack

Delay

Also: arrival time, time of arrival, delay compensation

Definition: The time offset between the reference signal and the measurement signal. It can include electronic processing, the loudspeaker's own response and acoustic travel through air; cross-correlation is one way of estimating it. Only the acoustic travel component converts directly to distance, using the speed of sound (about 343 m/s at 20 °C).
In plain words: How much later the sound arrives at the microphone than the reference, shown in milliseconds and as an equivalent distance.
In use: Find the delay before reading the transfer function, so both signals are compared over the same stretch of time. The distance shown is the equivalent path length of the whole delay; it equals the physical distance only when nothing but air travel separates the two signals. When aligning subwoofers and tops, check the arrival-time figures against the relative phase through the crossover region.

AcoustiTrack

Ducking

Definition: Automatic reduction of one signal's level while another signal is present, typically by a compressor driven from a sidechain, or by a gate or expander in a ducking (inverse) mode.
In plain words: One sound getting quieter automatically whenever another one plays.
In use: Ducking clears space — music under speech, a bass under the kick. Pumping can come from an ordinary compressor too, but when something pumps in time with another part, a sidechain is a likely cause; following the routing to its source is how you find it.

SessionMap

Dynamic range

Definition: The ratio, usually in decibels, between the highest level a system can handle within a stated distortion limit and its noise floor, measured under stated conditions.
In plain words: The span between the quietest sound a device can show above its own hiss and the loudest it can take before it distorts.
In use: A property of the equipment — interface, microphone, preamp. A measurement needs both the signal and the noise it is compared with to sit inside it. Signal-to-noise ratio is the margin a particular measurement achieves within that span.

E

EDT

Also: early decay time

Definition: Early decay time: the decay rate of the Schroeder decay curve between 0 dB and −10 dB, obtained by a least-squares straight-line fit and extrapolated to a 60 dB decay, in seconds (ISO 3382-1).
In plain words: How quickly the first part of the reverberation dies away — the part a listener actually hears while music or speech carries on.
In use: EDT follows what people perceive as reverberance more closely than T20 or T30, and it changes from seat to seat. Read it at several positions: a seat with a short EDT close to the stage and a long one under a balcony explains why the same room sounds different in different places.

AcoustiTrack

Energy-time curve

Also: ETC

Definition: The energy envelope of the impulse response — the squared response, smoothed, or the squared magnitude of its analytic signal — plotted in dB against time.
In plain words: The impulse response drawn as energy in decibels, so each reflection shows as a distinct peak above the decay.
In use: A clear view for finding individual reflections: take the time of a strong peak minus the time of the direct sound, multiply by the speed of sound, and you have the extra distance it travelled — then find the surface responsible. Different ways of building the envelope give slightly different curves.

AcoustiTrack

F

FFT

Also: fast Fourier transform, FFT size

Definition: Fast Fourier transform: an efficient algorithm for computing the discrete Fourier transform, which turns a block of N time samples into N frequency bins spaced at the sample rate divided by N.
In plain words: The mathematics that turns a slice of sound into its separate frequencies, so the analyser can show how much of each is present.
In use: Larger FFT sizes use a longer stretch of signal, which generally separates low frequencies more finely but takes longer to observe; smaller sizes react faster. How often the screen updates also depends on overlap and processing. 16,384 points at 48 kHz gives bins about 2.9 Hz apart.

AcoustiTrack

Frequency bin

Also: FFT bin, bin width, bin spacing

Definition: One output point of a discrete Fourier transform. Bins are spaced Δf = fs / N apart, where fs is the sample rate and N the transform size.
In plain words: One of the evenly spaced frequency points the FFT calculates. The spacing sets where the spectrum is sampled; telling two close frequencies apart also depends on how long the measurement is and on the window.
In use: At the bottom of the range a narrow fractional-octave band can be narrower than one bin; a larger FFT size gives it enough bins to be measured. Padding a block with zeros draws bins closer together but does not separate frequencies any better.

AcoustiTrack

Frequency weighting

Also: A-weighting, C-weighting, Z-weighting, dB(A), dB(C), dBA, dBC

Definition: Standard frequency responses applied to a sound level measurement, defined in IEC 61672-1: A-weighting strongly reduces low frequencies, following the ear's sensitivity at moderate levels; C-weighting is nearly flat with gentle roll-offs at the extremes; Z-weighting is flat over its specified range.
In plain words: Filters that decide how much each part of the frequency range counts in a level reading. A is shaped after the ear at moderate levels; C keeps the bass; Z counts everything equally.
In use: Use the weighting the rule is written in — most noise limits and exposure rules use A, and some add C-weighted peak limits. Use C to see the low end that A hides; C − A shows how much of a level is bass. Use Z for an unweighted reading.

AcoustiTrack

G

Goniometer

Also: vectorscope, stereo vectorscope

Definition: An X–Y display of the left and right sample values, rotated 45° so that a mono signal draws a vertical line and a signal opposite in polarity between the channels draws a horizontal one.
In plain words: A picture of the stereo image: a narrow upright shape is close to mono, a wide cloud is a wide stereo image.
In use: Shows the shape behind the correlation meter's single number: how wide a track is, whether it leans to one side, and whether part of it spreads sideways into opposite polarity. TrackScope draws it for the selected track in its Phase view.

TrackScope

Group delay

Definition: The negative derivative of phase with respect to angular frequency, τg(ω) = −dφ/dω, giving the time delay of the signal's envelope at each frequency.
In plain words: How late each part of the frequency range arrives, in milliseconds.
In use: Turns a phase trace into time: a pure delay reads as one constant figure at every frequency, while a crossover or a sub shows as frequencies that arrive later. In a room, interference can produce very large or even negative values that are not real travel times, so read it on clean, well-behaved parts of the response.

AcoustiTrack

I

Impulse response

Also: IR

Definition: The output of a linear time-invariant system when driven by a unit impulse. It describes the system completely in the time domain and forms a Fourier-transform pair with the transfer function.
In plain words: What a room and loudspeaker system do to a single, instantaneous click: the direct sound, then every reflection, then the decay.
In use: The basis of the room-acoustics figures: arrival time, reflections, decay times and clarity are calculated from it, and speech intelligibility too when speech level and background noise are added. Look at it directly to find a strong late reflection or an echo.

AcoustiTrack

Insert effect

Also: inserts, insert effects, insert slot, insert slots

Definition: A processor placed directly in a channel's signal path, so that the whole signal passes through it in series — as opposed to a send, which feeds a copy of the signal to a shared effect.
In plain words: An effect plugged straight into a channel, so everything on that channel goes through it — an EQ or a compressor, for example.
In use: Inserts process the signal one after another, top to bottom, so their order changes the sound. In Logic Pro the pan knob acts after the inserts, so a plug-in in an insert slot does not hear it. TrackSpace's probe goes in the last insert slot, where it hears what the channel's plug-ins produce.

TrackSpace

L

L10, L50, L90

Also: L10, L50, L90, percentile levels, statistical levels, LN

Definition: Percentile (statistical) levels: LN is the sound level exceeded for N percent of the measurement period. L10 is exceeded 10 % of the time, L50 half the time, L90 90 % of the time.
In plain words: L10 describes the louder parts, L50 the typical level, and L90 the quieter level underneath.
In use: L90 is often used as an estimate of background noise and L10 of the louder programme — neither is a peak reading. State the frequency weighting and how often the level was sampled. Logging them over a show shows how level varied, not only its average.

AcoustiTrack

LAeq

Also: LAeq,15min, LAeq,T

Definition: The A-weighted equivalent continuous sound level over a stated period T, for example LAeq,15min (IEC 61672-1).
In plain words: The A-weighted average level over a set time, the number venue noise limits are usually given in.
In use: Venue limits are often written as an LAeq over a fixed period, for example 100 dB LAeq,15min in some licences — check the actual rule. Know whether the period is fixed (clock quarter-hours) or rolling; watching it during the show tells you how much room is left before the period ends.

AcoustiTrack

Leq

Also: equivalent continuous sound level, Lp,eq, energy average

Definition: Equivalent continuous sound level: the level of a steady sound that, over the same period, would contain the same acoustic energy as the fluctuating sound measured, in dB.
In plain words: The average level over a period, worked out from the sound's energy, so short loud moments weigh far more than long quiet ones.
In use: The figure many noise limits and exposure rules are written in. Read it over the period the rule names; rules that also set peak limits or use another exchange rate need those checked as well.

AcoustiTrack

M

Magnitude

Also: magnitude response

Definition: The absolute value of the complex transfer function, |H(f)|, usually expressed in dB; 0 dB means unity gain relative to the reference at that frequency. The phase can still differ.
In plain words: How much louder or quieter each frequency arrives at the microphone than it went into the system.
In use: The curve you EQ against. Peaks and dips show where the system and room boost or cut; compare it with a target curve and correct broad trends rather than every narrow dip, which usually belongs to one microphone position.

AcoustiTrack

Maximum linear SPL

Also: maximum SPL, max SPL, AES75

Definition: The highest measured output level at which a loudspeaker system still meets specified linearity criteria under stated test conditions. AES75 defines a method using its M-Noise test signal: the level is raised in steps and each step's response is compared with a low-level reference; the last step within tolerance is the maximum linear level.
In plain words: How loud a system can play before it starts changing the sound — compressing, distorting or protecting itself.
In use: Report the test signal, distance, frequency range, level metric and limiting criteria with the figure. AcoustiTrack measures in the manner of AES75 but drives the system with its own pink or speech-shaped noise, so its result is "AES75-style", not an AES75 measurement. Measure under controlled conditions; one figure does not establish the headroom at every seat.

AcoustiTrack

Measurement microphone

Also: measurement mic, correction file, microphone correction, calibration file

Definition: An omnidirectional microphone with a flat, stable and documented frequency response, made to measure sound rather than to record it. Many are supplied with a correction file describing that unit's measured response.
In plain words: A small, neutral microphone built to measure the room with as little colouring of the sound as possible.
In use: If the maker supplies a correction file (.txt, .csv, .frd, .cal or .dat), load the one that matches the microphone and the way it is pointed, so the analyser removes its documented deviations. Calibrate the chain on an acoustic calibrator so levels read in dB SPL.

AcoustiTrack

Measurement uncertainty

Also: uncertainty of measurement

Definition: A non-negative parameter characterising the dispersion of the values that can reasonably be attributed to the quantity being measured, based on the information used (JCGM 100, the GUM; VIM 2.26).
In plain words: How far a reading could reasonably be off — the "±" that belongs with any measured number.
In use: Take it into account whenever a result is compared with a limit or a specification: 99 dB with ±1 dB of uncertainty, against a 100 dB limit, is not a clear pass. Calibration, microphone position, background noise and averaging all contribute.

Mono compatibility

Also: mono compatible, mono-compatible

Definition: The degree to which a stereo signal keeps its level and tonal balance when its left and right channels are summed to one; components opposite in polarity between the channels cancel in the sum.
In plain words: Whether a stereo track still sounds right when it is played back as one channel — on a phone speaker, a mono club system or a radio.
In use: Stereo wideners, microphones out of polarity with each other and some reverbs can sound wide in stereo and thin out or vanish in mono. A correlation meter sitting below zero is the warning sign; listening in mono confirms it before the mix ships.

TrackScope

Multi-time window

Also: MTW, multi-time-window

Definition: A transfer-function measurement that uses different FFT lengths in different frequency ranges — long windows at low frequencies, short at high — and splices them into one trace, for near-constant resolution per octave.
In plain words: A way of measuring that looks long at the bass and short at the treble, so each part of the range is seen at the right level of detail.
In use: Lets the high frequencies be analysed over shorter time spans, so less of the late room sound enters them, while keeping full detail in the bass. A short window reduces the influence of late reflections; it does not isolate the direct sound on its own.

AcoustiTrack

N

Narrowband spectrum

Also: narrowband, per-bin spectrum

Definition: The spectrum shown at the analyser's full resolution, one value per FFT bin, without combining bins into bands.
In plain words: The most detailed line the analyser can draw, one point per frequency bin.
In use: Shows narrow peaks, hum and its harmonics, and fine structure the bands average away. How high it sits relative to the band bars depends on how each display is scaled.

AcoustiTrack

NIOSH

Also: NIOSH REL

Definition: The US National Institute for Occupational Safety and Health recommended exposure limit (REL): 85 dB(A) as an 8-hour time-weighted average with a 3 dB exchange rate — each 3 dB increase halves the recommended time.
In plain words: A US occupational recommendation for daily noise exposure: 85 dB(A) for a full working day, half the time for every 3 dB louder. It is a recommended limit, not a guarantee that hearing cannot be harmed.
In use: The stricter of the two common US criteria and the one that tracks hearing risk more closely. Use it to manage exposure for crews and musicians over a long day; the measurement must represent the sound where those people actually are.

AcoustiTrack

Noise dose

Also: daily noise dose, noise exposure

Definition: The accumulated noise exposure expressed as a percentage of the reference daily exposure under the selected assessment method; 100 % corresponds to the criterion level sustained for 8 hours under the stated exchange rate and threshold.
In plain words: How much of the reference daily noise exposure has been reached so far, as a percentage. 100 % means that reference exposure has been reached; it is not a line between harmless and harmful sound.
In use: State the rule with the figure — criterion level, exchange rate, threshold and measuring time — because NIOSH and OSHA give different numbers for the same day. A microphone in one place measures exposure in that place; to assess a person, measure where that person works for the period that matters.

AcoustiTrack

O

Octave and fractional-octave bands

Also: octave band, third-octave, 1/3 octave, one-third octave, fractional-octave, 1/1 octave

Definition: A band whose upper edge is twice its lower edge is one octave wide; a 1/b-octave band spans a frequency ratio of G^(1/b), where G is the octave ratio (10^0.3 ≈ 1.995 in IEC 61260-1, or exactly 2 in the base-2 system). Band centres are referenced to 1 kHz — a centre for odd b, a band edge for even b in IEC 61260-1.
In plain words: Slices of the frequency range that each cover the same musical interval — an octave, or a third of one — matching the way the ear hears pitch.
In use: Third-octave bands are the standard view for tuning a system: wide enough to read the tonal balance at a glance, fine enough to place an EQ move. Go to 1/12 or 1/24 octave to find a narrow resonance; go to whole octaves to compare rooms or report decay times.

AcoustiTrack

OSHA

Also: OSHA PEL, OSHA hearing conservation

Definition: The US federal general-industry noise standard (29 CFR 1910.95), which uses a 90 dB(A) criterion for 8 hours and a 5 dB exchange rate. For the permissible exposure limit (PEL) levels below 90 dB(A) are not counted; for hearing-conservation assessment levels below 80 dB(A) are not counted, and the hearing-conservation programme is required from an 8-hour time-weighted average of 85 dB(A).
In plain words: The US workplace noise rule: 90 dB(A) for a full day, half the time for every 5 dB louder — counted one way for the legal limit and another way for hearing protection.
In use: Use it where a US workplace rule applies or a client asks for it, and say which form you report. AcoustiTrack's OSHA dose uses the hearing-conservation settings: criterion 90 dB(A), 5 dB exchange rate, 80 dB(A) threshold. Other countries and workplaces have their own rules.

AcoustiTrack

P

Pan

Also: panning, panned, pan knob, pan position, pan positions

Definition: The placement of a signal between the left and right loudspeakers, set by feeding it to the two channels at different levels according to a pan law; on a stereo channel the same control usually acts as a balance control.
In plain words: Where a sound sits from left to right between your two speakers.
In use: Panning spreads instruments across the stereo field so they do not all compete in the middle. In Logic Pro the pan knob acts after the channel's inserts, so no plug-in on the channel hears it; TrackSpace reads the real pan positions from Logic Pro directly and combines them with the balance it measures.

TrackSpace

Peak hold

Definition: A display trace that holds the maximum level reached in each band or bin since it was last reset, or that falls back at a set rate.
In plain words: A line that remembers the loudest each frequency has been.
In use: Catches events the live bars have already let go of: a feedback ring, a short loud hit, a resonance excited for an instant.

AcoustiTrack

Peak level

Also: sample peak, peak reading

Definition: The highest instantaneous absolute value of a signal over the measuring interval, in dB, with no time averaging. Sample peak, reconstructed true peak and acoustic peak are different measurements.
In plain words: The very highest point the signal reaches, rather than an average.
In use: Read it beside Fast or Slow to see roughly how far the peaks rise above the average level and how much headroom the system still has; this difference is not a precisely defined crest factor.

AcoustiTrack

Phase

Also: phase response

Definition: The argument of the complex transfer function, ∠H(f), in degrees; it describes the timing relationship between the output and the input at each frequency.
In plain words: Whether each frequency arrives in step with the reference or ahead or behind it.
In use: The key to aligning loudspeakers that play the same frequencies — a sub and a main, a main and a fill. Where their phase traces match through the crossover region and their levels are similar, they add up; where they are opposed they cancel. A pure delay wraps the phase at even spacing on a linear frequency axis, which looks like faster and faster wrapping toward the treble on a log axis.

AcoustiTrack

Pink noise

Definition: Random noise whose power spectral density is inversely proportional to frequency (1/f), falling 3 dB per octave, so that every octave carries equal power.
In plain words: A rushing noise with the same energy in every octave, which sounds balanced to the ear.
In use: The standard test signal for tuning a system: it excites the whole range evenly in the way fractional-octave bands divide it, so a properly scaled RTA shows a flat line for a flat system and a flat signal chain.

AcoustiTrack

Polarity

Also: polarity reversal, polarity inversion, reversed polarity

Definition: The sign of the relationship between an electrical signal and the sound it produces: with positive polarity a positive voltage at the input produces a positive pressure. Reversing polarity inverts the waveform — the same as a 180° phase shift at every frequency.
In plain words: Whether a loudspeaker pushes air out or pulls it in when the signal goes positive. Two speakers wired opposite ways fight each other.
In use: Reversed polarity changes how a loudspeaker combines with its neighbours: where they play the same frequencies the result depends on their existing phase and level relationship — it can cause cancellation, and sometimes improves the sum at a crossover. In a transfer function it shows as the phase trace moved by 180°; decide at the processor or amplifier, and measure again.

AcoustiTrack

Power averaging

Also: energy averaging, power average

Definition: Averaging the squared magnitudes (energy) of several readings and converting the result back to a level. Distinct from magnitude averaging, which averages linear amplitudes, and from decibel averaging, which averages the levels in dB; when the readings differ, the power average is the highest of the three and the decibel average the lowest.
In plain words: Averaging by energy, so louder readings count for more — the way sound adds up in the air. Averaging the decibel numbers instead gives a lower figure whenever the readings differ.
In use: Know which method is in use before comparing averages from two tools: with widely varying readings the methods can differ by several dB. Complex averaging, which also keeps phase, answers a different question again.

Pseudorandom noise

Also: periodic noise, periodic pink noise, MLS

Definition: A deterministic noise sequence that repeats exactly after a fixed number of samples — for example periodic pink noise or a maximum-length sequence (MLS). When the analysis block equals its period and the system has settled, every block contains the same spectrum.
In plain words: A noise signal that repeats itself exactly, so the measurement settles almost at once.
In use: Gives a stable transfer function with little averaging when the period suits the FFT size and the system is steady, which saves time when each position must be measured quickly.

AcoustiTrack

R

Reference signal

Also: loopback, loopback reference, Y-split

Definition: In dual-channel measurement, the copy of the excitation signal fed directly to the analyser, against which the microphone signal is compared to obtain the transfer function.
In plain words: A clean copy of the test signal, taken before the loudspeaker, so the analyser knows what the system was sent.
In use: An electrical loopback — a cable from the output into a spare input — gives a clean timing and signal reference. Delays shared by both paths, such as the interface's own latency, cancel in the comparison; everything after the point where the reference is taken — processor, amplifier, loudspeaker and air — remains part of the measured system.

AcoustiTrack

Return

Also: effects return, aux return, reverb return, returns

Definition: The channel that brings the output of a shared effect, fed by sends, back into the mix — in Logic Pro, the aux channel strip on the bus the sends feed.
In plain words: The channel where an effect such as a reverb comes back into the mix, so you can set how much of it you hear.
In use: The return's fader sets the overall amount of that effect in the mix; each track's send sets how much of that track goes into it. Following a return back to its sends shows which tracks share the effect.

SessionMap · TrackSpace

RMS

Also: root mean square, RMS level

Definition: Root mean square: the square root of the mean of the squared instantaneous values of a signal over a stated time interval. For a sine wave it equals the peak value divided by √2.
In plain words: A way of stating a signal's level that follows its power rather than its highest peaks — usually what a meter or a specification means by "level".
In use: Compare RMS with RMS and peak with peak. Test-signal, noise and amplifier levels are normally stated as RMS; how far the peaks rise above it is the crest factor.

RT60

Also: reverberation time, T60, decay time

Definition: The time, in seconds, for the sound pressure level in a room to fall by 60 dB after a sound source stops (ISO 3382-1). In practice it is evaluated over a shorter range of the decay and extrapolated to 60 dB — see T20 and T30.
In plain words: How long a room keeps ringing after a sound stops. A large hall can take two seconds or more; a treated control room a fraction of a second.
In use: The first number to look at when a room sounds boomy, washy or dead. Read it per octave band: a low-frequency decay much longer than the mids often points to a room that needs bass treatment. In small rooms the bass is dominated by individual modes, where a single reverberation time describes the room less well.

AcoustiTrack

RTA

Also: real-time analyser, real-time analyzer

Definition: Real-time analyser: an instrument that continuously displays the level of a signal in each of a set of frequency bands, typically fractional-octave bands, as the signal occurs.
In plain words: A live picture of how loud each part of the frequency range is, right now.
In use: Use it to hear with your eyes: find the frequency of a ring, a boom or feedback, check a microphone is alive, see the noise floor of a room before doors, or compare what a source produces with what you expect.

AcoustiTrack

S

Sample rate

Also: sampling rate, sampling frequency

Definition: The number of samples per second at which an audio signal is digitised, in hertz. The highest frequency it can represent is half the sample rate (the Nyquist frequency).
In plain words: How many times per second the audio interface takes a reading of the sound — 48,000 times at 48 kHz.
In use: 48 kHz covers the audible range and is the usual choice for measurement. Keep it the same for a job: an FFT's bin spacing is the sample rate divided by the FFT size, and changing the rate or interface settings can change the chain's level calibration, so check it again. A microphone's correction file is not tied to a sample rate.

AcoustiTrack

Schroeder curve

Also: Schroeder integral, backward-integrated decay curve, decay curve

Definition: The energy decay curve obtained by integrating the squared impulse response backwards in time from its end (Schroeder, 1965), expressed in dB relative to the total energy. It equals the ensemble average of many interrupted-noise decays.
In plain words: A smooth line showing how much sound energy is still to come at each moment after the direct sound, falling as the room goes quiet.
In use: The decay times are fitted on this line. A straight line suggests one even decay rate; a bend can mean two rates — for example a lively stage coupled to a drier audience area — but it can also come from background noise or where the response was cut off, so check those first.

AcoustiTrack

Send

Also: aux send, aux sends, sends, effects send

Definition: A secondary output on a channel strip that routes a copy of the channel's signal, at an adjustable level, to a bus while the channel's main output continues unchanged.
In plain words: A knob on a track that sends a copy of its sound somewhere else — often to a reverb — while the track itself keeps playing as normal.
In use: Sends feed shared effects, headphone mixes and sidechains. Each send can sit before or after the channel fader. SessionMap draws sends as dashed lines, and flags a send whose destination is missing or unassigned.

SessionMap

Sidechain

Also: side-chain, side chain, key input

Definition: The detector path of a dynamics processor, such as a compressor or gate, which decides when it acts. It is fed by the processor's own input by default, or by another signal through an external sidechain (key) input.
In plain words: The part of a processor that listens and decides when to act — normally to the sound it processes, or with an external sidechain to a different sound, such as the kick telling a compressor on the bass when to squeeze.
In use: Sidechains make kick and bass share space, make music duck under a voice-over and key gates. In Logic Pro the source is chosen in the plug-in header's Side Chain menu, one plug-in at a time, which is why a sidechain is hard to find by looking at the mixer.

SessionMap

Signal flow

Also: signal path

Definition: The path an audio signal takes from its source through processors and busses to its destinations — the main mix, a hardware or monitor output, a recording destination or a sidechain.
In plain words: Where the sound goes: from each track, through whatever it is sent to, until it reaches an output.
In use: Following the signal flow is how you find out why a track is too quiet, doubled or missing. SessionMap draws it as a map: solid lines are outputs, dashed lines are sends, and selecting a channel shows the path it takes through the session.

SessionMap

Signal-to-noise ratio

Also: SNR, S/N, signal-to-noise

Definition: The ratio of the level of a wanted signal to the level of the background noise present with it, in a stated bandwidth and under stated conditions; usually expressed in decibels as the difference between the two levels.
In plain words: How far the sound you are measuring stands above everything else — hum, hiss, air conditioning, the audience.
In use: Check the background level with the test signal off before trusting a reading. Reverberation measurements need a clear margin: about 35 dB for T20 and 45 dB for T30 (ISO 3382-1). Too small a margin tends to show as ragged or unstable results.

Smoothing

Also: fractional-octave smoothing

Definition: Averaging of a frequency response over a sliding window of constant relative width, 1/N octave, around each frequency.
In plain words: Evening out the fine ripples in a curve so its overall shape is easier to read.
In use: Use 1/3 octave to see the tonal balance and 1/12 or 1/24 octave for detailed EQ work. In AcoustiTrack smoothing applies to the display; captures and the analysis keep the unsmoothed data.

AcoustiTrack

Spatial averaging

Also: spatial average, averaging microphones, mic averaging

Definition: Combining measurements from several positions to describe a listening area. Magnitude responses can be combined as a power, linear-magnitude or decibel mean, with stated weights per position; complex averaging across positions is also possible but includes phase-dependent cancellation and answers a different question.
In plain words: Several microphones placed around the room, combined into one response that describes the area rather than one seat.
In use: Tune to the trend in the average, not to one seat: a dip at one position is often a local cancellation that EQ cannot fix. An average can also hide a poor seat and still contains room effects, so look at the individual positions too. AcoustiTrack's "Average mics" takes an equal-weight power mean of magnitude.

AcoustiTrack

Spectrograph

Also: spectrogram

Definition: A display of a signal's spectrum against time — a spectrogram: frequency on one axis, time on the other, and level shown as colour or brightness. A waterfall plot is a related display that draws successive spectra as a 3D surface.
In plain words: A scrolling picture that shows which frequencies were present and how loud they were, moment by moment.
In use: Shows what a single spectrum cannot: a resonance that rings on, feedback building up, a hum that comes and goes. Each event leaves a trail you can point at and read the frequency of.

AcoustiTrack · TrackScope

Stereo Out

Also: stereo output, main output, mix output

Definition: In Logic Pro, the output channel strip that carries the final stereo mix to the audio interface and to bounces; tracks and auxes are assigned to it by default.
In plain words: The last stop: the channel the finished stereo mix leaves through.
In use: The usual destination of the mix. Routing that should reach the mix but never arrives here — a bus with no output, an aux assigned to nothing — is a dead end; signals can also leave on other outputs on purpose, such as monitor mixes or hardware outputs.

SessionMap

Stereo width

Also: stereo image, stereo spread

Definition: The apparent spread of a source across the stereo field, set by how much its left and right channels differ: identical channels image as a single point, decorrelated channels spread wider.
In plain words: How wide a sound seems between your speakers — from a single point in the middle to filling the whole space from left to right.
In use: Width gives a mix space: pads, room microphones and stereo reverbs are usually wide, while kick, bass and lead vocal usually stay narrow and centred. Widening a sound moves its two sides further apart, which can cost level in mono, so check it on a correlation meter. On TrackSpace's stage a mono source stays a point and a wider image is drawn wider.

TrackSpace

STI

Also: speech transmission index, speech intelligibility

Definition: Speech Transmission Index: a value from 0 to 1 describing how well a transmission channel preserves the intensity modulations of speech, computed from the modulation transfer function in seven octave bands (125 Hz to 8 kHz) at fourteen modulation frequencies (0.63 to 12.5 Hz), per IEC 60268-16.
In plain words: A single score for how intelligible speech will be at a listening position, from 0 (unintelligible) to 1 (perfect).
In use: The standard figure for voice alarm, public address and speech venues. Measure under representative speech level and background-noise conditions; with impulse-response methods, document how speech level and noise are included — without them the result describes the room alone and is an upper bound. Compare the result with the project's own specification rather than one universal pass mark.

AcoustiTrack

STIPA

Also: STI-PA, STI for public address

Definition: Speech Transmission Index for Public Address systems: the simplified direct method of IEC 60268-16, using a test signal of seven octave bands of noise, each modulated at two modulation frequencies, measured through the system to give an STI value.
In plain words: A quick way to measure STI by playing a special test signal through the sound system itself and listening to it at the seats.
In use: Useful for checking a PA or voice alarm system as installed. The result covers the part of the chain the test signal actually passes through: injected electrically it skips the announcement microphone; played acoustically into that microphone it includes it. State which, and measure with representative background noise.

AcoustiTrack

Swept sine

Also: sweep, sine sweep, exponential sweep, log sweep, ESS

Definition: An excitation signal whose frequency changes continuously over time, linearly or exponentially; the recorded response is deconvolved with the inverse sweep to obtain the system's impulse response. With an exponential sweep (Farina's method), harmonic distortion separates in time from the linear response.
In plain words: A test tone that glides from low to high, from which the room's impulse response is worked out.
In use: A common way to measure room acoustics: it gives a high signal-to-noise ratio for a short playing time, and with an exponential sweep the loudspeaker's harmonic distortion is separated from the room's response. Averaging several sweeps lowers background noise further.

AcoustiTrack

T

T20

Also: T-20

Definition: Reverberation time evaluated from the Schroeder decay curve between 5 dB and 25 dB below the initial level, by a least-squares line, and extrapolated to a 60 dB decay (ISO 3382-1).
In plain words: The room's reverberation time, worked out from a 20 dB stretch of the decay — from −5 to −25 dB — so that it can be measured even when background noise hides the rest.
In use: The everyday reverberation figure: it needs roughly 35 dB between the signal and the noise floor, so it often reads well in a working venue. Enough dynamic range alone does not guarantee a good fit; check the decay curve.

AcoustiTrack

T30

Also: T-30

Definition: Reverberation time evaluated from the Schroeder decay curve between 5 dB and 35 dB below the initial level, by a least-squares line, and extrapolated to a 60 dB decay (ISO 3382-1).
In plain words: The room's reverberation time, worked out from a longer stretch of the decay than T20 — 30 dB of it.
In use: Use it where the signal stands well clear of the noise (about 45 dB). Because it covers more of the decay it describes the later reverberation; a T30 noticeably longer than T20 can mean a slower second decay, such as a coupled space, but check noise, filtering and the fit before concluding that.

Target curve

Also: house curve, X-curve, target curves

Definition: A reference frequency response that a tuned system is aimed at. Examples include a flat target, a house curve with low-end lift, and the X-curve — a specific cinema reference (SMPTE ST 202 / ISO 2969), flat to about 2 kHz and rolling off above.
In plain words: The shape you want the system's response to have, drawn behind the measurement for comparison.
In use: Many rooms sound best with some low-end lift and a gentle fall in the treble rather than a flat line. Measure under the conditions the target assumes, compare the magnitude with it, and correct broad trends — do not EQ every difference, and never boost into a cancellation dip.

AcoustiTrack

THD

Also: total harmonic distortion

Definition: Total harmonic distortion: the root-sum-square of the RMS amplitudes of the harmonics divided by the RMS amplitude of the fundamental, THD = √(V₂² + V₃² + … + Vₙ²) / V₁, often given in percent. THD+N is a separate measurement that includes noise in a stated bandwidth; its reference convention should be stated.
In plain words: How much a loudspeaker or device adds tones of its own — overtones of the test tone — that were not in the signal.
In use: Play a sine at a working level and read THD to check a driver or amplifier is clean; rising distortion as the level goes up shows where a system runs out of headroom.

AcoustiTrack

Time weighting

Also: Fast, Slow

Definition: Exponential averaging applied to the squared sound pressure in a sound level meter, defined in IEC 61672-1: Fast has a time constant of 125 ms, Slow a time constant of 1 s.
In plain words: How quickly a level reading follows changes: Fast moves with the music, Slow settles to a steadier figure.
In use: Fast is for watching a show and catching short loud moments; Slow is easier to read and is what many calibration and survey procedures specify. State which one you used when you compare readings with another meter.

AcoustiTrack

Transfer function

Also: frequency response, H1

Definition: The complex ratio of a system's output spectrum to its input spectrum, H(f), describing its gain and phase at every frequency. In dual-channel measurement it is estimated as H1 = Gxy / Gxx, the cross-spectrum of reference and measurement divided by the reference auto-spectrum.
In plain words: A picture of what a loudspeaker and the room do to a signal: which frequencies come out louder or quieter, and which arrive early or late.
In use: The core view for system tuning. Because it compares what goes into the system with what the microphone hears, it works with programme material as well as test signals — provided the signal has energy at the frequencies you read and the system stays steady. Read the magnitude to set EQ and the phase to align loudspeakers.

AcoustiTrack

True peak

Also: true-peak, dBTP, true peak level

Definition: An estimate of the maximum absolute value of the continuous signal that a digital signal represents, obtained by oversampling before peak detection (ITU-R BS.1770); expressed in dBTP. It can exceed the sample peak.
In plain words: The real top of the waveform, including peaks that fall between the samples — the level a converter actually has to reproduce.
In use: Use it for headroom wherever a signal is converted back to analogue or encoded: a signal can clip on playback even when every sample is below 0 dBFS. A plain sample-peak meter can read lower than the true peak.

W

White noise

Definition: Random noise with a flat power spectral density: equal power per hertz across the frequency range.
In plain words: A hissing noise with equal energy at every frequency, so most of its energy is in the treble.
In use: Used in electronics and for some narrowband tests. For room and loudspeaker work pink noise is the usual choice, because it spreads energy evenly per octave as the ear and fractional-octave bands do.

AcoustiTrack

Window function

Also: Hann, Hamming, Blackman-Harris, rectangular window

Definition: A weighting applied to each block of samples before the FFT. Tapered windows reduce the leakage caused by cutting the signal into blocks; the choice trades main-lobe width (resolution) against sidelobe level (leakage). A rectangular window applies no taper.
In plain words: A fade applied to each slice of sound before it is analysed, to limit how much frequencies smear into their neighbours.
In use: Hann is the usual choice. Hamming has lower near sidelobes but does not reach zero at the ends; Blackman-Harris lowers leakage further, to see a quiet tone beside a loud one; rectangular suits tones that fall exactly on a bin.

AcoustiTrack