Technical knowledge · HUB · REV 2026-10-06
Glossary
The glossary fixes meaning so RT60 is not used as isolation, and throw ratio is not used as brightness. The first batch is short on purpose.
What this gate is
Each entry: the name, the short phrase, and the limit. If a longer page exists, the link is under it.
Three hundred empty terms are worse than thirty that can be defended. Expansion arrives with the pages, not before them.
What is published now
Parameters
Parameters
Systems
Systems
Hall geometry
Hall geometry
Links
Links
When to open this gate
While reading a specification
While reading a specification
Before translating a meeting
Before translating a meeting
Not to write a contract clause from a glossary line
Not to write a contract clause from a glossary line
How to read the subject
- 01
Read the limit, not only the name.
- 02
Open the long page if it exists.
- 03
Do not copy a performance figure from the glossary, because it does not hold one.
- 04
If a term is missing it is on the map, or it has not been reviewed.
What this gate does not do
Equating STC with RT60
Equating STC with RT60
Translating line array as “a long speaker” and dropping the rest
Translating line array as “a long speaker” and dropping the rest
Treating the glossary as complete
Treating the glossary as complete
RT60
Reverberation time
The time for sound level to fall 60 dB after the source stops. Measured per ISO 3382. It changes with frequency, volume, and absorption.
Reverberation timeSTI
Speech transmission index
A 0-to-1 measure of speech modulation transfer, described in IEC 60268-16. Both noise and reverberation reduce it.
Speech transmission indexC50
Early clarity for speech
Ratio of energy arriving within 50 ms to later energy, in decibels. Used to discuss speech clarity. It does not replace STI.
Early clarity for speechC80
Clarity for music
The same idea as C50 with an 80 ms limit. More often discussed for music rooms.
Clarity for musicEDT
Early decay time
Decay of the early part of the decay curve, scaled for comparison with RT60. It relates more closely to the subjective sense of reverberance.
Early decay timeSabine
Sabine equation
RT = 0.161 V / A in metric units. Roughly usable when absorption is low and distributed. It is not a complete description of a real room.
Sabine equationSabin
Unit of absorption
One square-metre sabin equals one square metre of surface with an absorption coefficient of 1. The sum of sabins is A in the Sabine equation.
Unit of absorptionα
Absorption coefficient
The share of energy not reflected. It depends on frequency and mounting. A single number without a frequency and a laboratory report is not a specification.
Absorption coefficientSTC / Rw
Laboratory airborne insulation
Single-number ratings of laboratory airborne insulation. Field performance is usually lower because of flanking, openings, and services.
Laboratory airborne insulationNC / NR
Background noise
Curves for comparing a room-noise spectrum, not a single decibel figure. The acceptance target belongs in the project brief.
Background noiseLine Array
Line array
Vertically coupled elements shaped to steer energy. Not automatically the right choice for small rooms or nearby speech.
Line arrayPoint Source
Point source
A cabinet with fixed directivity. Often clearer in short rooms when it covers the seats without exciting the ceiling and walls.
Point sourceDante
Networked audio transport
A protocol for audio on a network. It does not replace clock, switch, and QoS design, and it is not the same thing as AES67.
Networked audio transportAES67
Audio-over-IP interoperability
A standard for exchanging audio between networked systems under stated conditions. Interoperability is tested, not assumed from a logo.
Audio-over-IP interoperabilityHearing loop
Hearing loop
A magnetic field carrying audio to a hearing-aid telecoil. Field performance is discussed against IEC 60118-4.
Hearing loopDMX
Lighting control data
A data protocol for lighting equipment. Distribution, protection, and device count on a line are part of the design, not a later detail.
Lighting control dataPixel pitch
Pixel pitch
Distance between pixel centres. It sets an approximate viewing distance together with brightness and content. It is not image quality by itself.
Pixel pitchThrow ratio
Throw ratio
Projector-to-screen distance divided by image width. Lens choice starts from room geometry, not from a single catalogue.
Throw ratioC-value
Sightline clearance
The vertical clearance by which a spectator sees over the person in front. Theatre literature often discusses about 90–120 mm, then project geometry and code fix the value.
Sightline clearanceTip-up
Tip-up seat
A pan that rises when the occupant leaves, widening the walking way. Clear width between tipped seats is what circulation uses, not only the open-pan width.
Tip-up seatTelescopic
Telescopic grandstand
Units that slide to open the stand or clear the floor. It needs storage, a floor that accepts the track, and maintenance of wheels and locks.
Telescopic grandstandFly system
Overhead flying system
Equipment for raising scenery, lights, and drapes above the stage. Load, safety factor, and who may move it are part of the design.
Overhead flying systemCyclorama
Cyclorama
A rear surface lit to read as an expanse. It needs lighting distance and freedom from shadow more than a handsome line on a drawing.
CycloramaBlack box
Flexible theatre
A neutral room whose audience and stage can be rearranged. Real flexibility is in power, audio, and rigging points, not in black paint.
Flexible theatreSTIPA
Abbreviated STI measurement
A shortened field method within the IEC 60268-16 family. Do not mix its result with a computer prediction without naming the method.
Abbreviated STI measurementQuestions designers and owners ask
How many terms?
How many terms?
Are brands named?
Are brands named?
Where do I add a term?
Where do I add a term?
Is the Arabic term enough?
Is the Arabic term enough?
Does the glossary translate the standards?
Does the glossary translate the standards?
Technical sources
- ISO 3382-1, IEC 60268-16 and IEC 60118-4
ISO 3382-1, IEC 60268-16 and IEC 60118-4
- Workshop usage
Workshop usage
- The library pages
The library pages
Last editorial review: 2026-10-06. Review means the text was checked, not that a project was measured.
Turn the question into a brief
A study starts from room volume, use, and existing condition, not from a product name. Fill the brief and copy it.
Project study form