Theatre Acoustic Design: The Complete Guide (2026)

By Daniel Natoli, Director, AKA Acoustics (MAAS, MAES). Last updated: 26 June 2026.

Theatre acoustic design tunes four interacting parameters across every seat: a reverberation time set to room volume, early-reflection energy inside the 50 ms window that lifts C50 and STI, airborne and impact isolation from foyer, street and plant, and a background-noise floor low enough to clear soft passages. Held in balance, the rear rows carry the same intelligibility as the front; missed, the room masks the consonants that carry the words.

A theatre is one of the hardest acoustic problems in a building, because the targets pull against each other and the room is judged live, in front of an audience, with no second take. This guide covers what makes a drama theatre acoustically good, how a theatre differs from an auditorium, what reverberation time it should have, how stage and audience acoustics work, how the room is isolated and made dual-purpose, what it costs in Australia, and who can design and build it from brief to a measured result. AKA Acoustics is a studio-born Sydney firm that designs, builds and supplies the acoustic products for a room under a single contract, then verifies the result by measurement to ISO 3382-1 rather than assuming it. This guide sits within our broader work on designing and building high-performance acoustic spaces, and alongside our auditorium acoustic design guide.

What is the difference between a theatre and an auditorium?

A theatre and an auditorium are tuned to different targets. A theatre is a staged-drama room, usually proscenium-fronted and speech-led, so it runs a shorter reverberation time of about 1.1 to 1.2 seconds unoccupied to hold C50 and STI for the spoken word. An auditorium is a broader, often music-capable assembly hall, so it carries a longer reverberation time led by EDT and C80. Serving both in one room needs variable acoustics.

What makes a drama theatre acoustically good?

Speech intelligibility governs a drama theatre. Every seat needs direct sound reinforced by early reflections inside the first 50 ms, integrating to hold C50 above 0 dB and STI past 0.60, over a noise floor low enough not to mask consonant onsets, with reverberation set to room volume. Meet all four and an unamplified voice carries to the rear rows; miss one and intelligibility falls below the threshold of effortless comprehension.

Four levers set whether a theatre works, and they interact:

• Intelligibility and early reflections. Direct sound from the stage must reach every seat, reinforced by early reflections off the ceiling, side walls and proscenium inside about 50 ms. Energy arriving later smears speech and pulls C50 down rather than supporting it.
• A volume-dependent reverberation time. Reverberation is tuned to room size and use. Set it too long and late energy masks the consonant onsets, pulling C50 and STI down; set it too short and early-decay support and sound strength G collapse, leaving the voice thin and unprojected at the rear.
• Stage-to-audience coverage and geometry. The seating rake, the room shape and the sightlines are set so the direct sound and the useful early reflections reach every seat, not just the favoured central ones, holding sound strength G across the seating plane.
• Isolation from everything else. Noise from the foyer, the street, the back-of-house and the mechanical plant is held outside the room by mass and decoupling, so the quiet moments on stage land against silence rather than a hum.

The common thread is that these are solved together, against numbers, before a wall is built. Lift the absorption to shorten reverberation and you weaken the early reflections that carry C50; open the room up for those reflections and you can lose the isolation that protects the noise floor. A good theatre design holds all four in balance and verifies it by measurement, not assumption.

What reverberation time should a theatre have?

There is no single fixed reverberation time for a theatre; it scales with room volume per the AS/NZS 2107:2016 guidance. A drama theatre of roughly 4,500 to 5,000 cubic metres maps to about 1.1 to 1.2 seconds unoccupied; survey data clusters near 1.0 second, and an occupied room runs about 0.3 seconds shorter as audience absorption is added.

Reverberation scales with room volume, which is why no single number fits every theatre. AS/NZS 2107:2016 sets auditoria reverberation through volume-dependent guidance, reverberation time against room volume at mid-frequency, with speech and lecture spaces sitting shorter than music spaces. A larger room is allowed, and needs, a longer reverberation time than a small one. For concert, recital and opera rooms the standard defers to specialist advice rather than a tabled value.

The reason reverberation scales with volume is that a bigger room takes longer for sound to decay through repeated reflections, and the design has to allow for that rather than fight it. Independent acoustics literature points to a useful sizing ratio of roughly 4 to 7 cubic metres per seat for a drama theatre, which ties seat count, room volume and reverberation target together. The table below shows how the target moves with volume rather than sitting at a single value.

Two points for buyers. First, reverberation is read off the volume-dependent guidance against the real room volume, then proven room by room, not copied from a table. Second, speech targets run shorter than music targets, which is exactly why a room built for both needs variable acoustics, covered below.

How do stage and audience acoustics work in a theatre?

Stage and audience acoustics work by delivering direct sound and its early reflections to every seat inside the 50 ms intelligibility window. Seating rake and room geometry hold the direct path unblocked and raise sound strength G at the rear; ceiling, proscenium and side-wall reflections arrive early enough to integrate rather than blur; controlled reverberation and a low noise floor preserve C50 across the full seating plane.

The measures that describe this are set out for performance spaces in ISO 3382-1:2009, and they are the design objective that drives the room shape. Speech Transmission Index (STI) runs on a 0 to 1 scale, where about 0.5 is marginal and 0.6 or better is the design aim for a speech audience, with 0.7 and above counting as good. C50, the early-to-late sound ratio, is recommended above 0 dB for speech, meaning more useful early energy reaches the listener than late, blurring energy. Both depend on the 50 ms early-reflection window: sound inside it builds intelligibility, sound after it erodes it. The table sets out what each lever does.

The design discipline is to model these before the room is built, then measure them in the finished room, verified to ISO 3382-1 rather than asserted. AKA's measured base for this discipline is its critical-listening rooms, including its own Kiln Studios Dolby Atmos control room, where the same spatial-averaging measurement approach proves the room a listener actually hears.

How do you isolate a theatre from foyer, street and plant rooms?

Theatre isolation is a separate problem from the in-room reverberation target, and it sits on the mandatory side of the standards. Isolation is achieved with mass and decoupling: mass-air-mass partitions and structural breaks that raise the field-verified Dn,T,w and L'nT,w between the theatre and its foyer, street and plant, not only the laboratory Rw and Ln,w. The result is set by the weakest path, and that path is rarely the wall - it is the door seal, the airlock, and the flanking transmission through floor, ceiling and the services around the partition.

The National Construction Code sets the floor for that isolation: minimum airborne (Rw, and Rw plus Ctr) and impact (Ln,w) sound-insulation requirements enforced at building approval. In a theatre the weakest element is almost always the door. A wall can be built to a high rating, but a poorly detailed door, or the gap under it, leaks sound straight past the wall it sits in. On a northern-beaches live-music hotel, an AKA acoustic door was fitted at Rw 48 against an Rw 46 requirement and held the line, and adding 140 patrons moved the measured L10 by only 2.4 dB because the PA, not the crowd, was the dominant source. Because AKA models, builds and field-measures the isolation under one contract, the field-verified result is owned by the team that detailed the door, not argued over after a handover. The same weakest-link discipline applies to a theatre: the door, the airlock and the service penetrations decide whether the wall rating means anything.

The four isolation paths a theatre design has to close, separately from its reverberation target:

• Foyer and back-of-house. Crowd, bar and circulation noise held out by rated walls, doors and airlocks, with the door detailing as the weakest link.
• Street and external. Traffic and external event noise stopped by the building envelope, and the theatre's own emission held to any consent or licence limit on the way out.
• Plant and mechanical. HVAC, pumps and switchroom noise isolated and silenced so they do not raise the in-room background-noise floor.
• Adjacent tenancies and dwellings. Where the theatre sits near homes or other tenancies, the NCC airborne and impact minimums apply between them.

AKA also designs to hard external limits where the site demands it: at a heritage venue inside a national park, the work was held to a strict external noise limit, the same discipline a theatre needs when its emission to a street or a neighbour is capped by a consent condition.

Can one theatre work for both drama and music?

Yes, through variable acoustics. A multipurpose room shifts mid-band reverberation between two regimes a single fixed RT cannot serve: a shorter speech setting led by C50 and STI, and a longer music setting led by EDT, C80 and early lateral energy for reverberance and spaciousness. Deployable absorption and coupled volume move the room between them, each setting modelled before build and measured at commissioning so both land, not only the default.

The tools that do this are deployed in combination and set during commissioning:

• Retractable absorption. Banners, drapes or roller absorbers that deploy to add absorption for a speech setting and retract to expose harder, more reflective surfaces for music.
• Adjustable panels. Rotating or hinged elements that present an absorptive face or a reflective face depending on the programme.
• Coupled volume. A secondary volume, such as a reverberation chamber, opened to lengthen the decay and EDT for music and closed for speech.
• Orchestra shell. A demountable shell that projects orchestral sound forward and adds the reflective surfaces a music programme needs, removed for a speech or drama setting.

What matters is the mechanism and the direction of change, not a fixed switchable pair. The room moves from a shorter speech setting, in the AS/NZS 2107 speech class, toward a longer music setting, and exactly how far depends on the room volume, the absorption budget and the brief. Designing variable acoustics well means modelling both settings before building and measuring both at commissioning, so each one lands rather than only the one the room defaults to.

What does theatre acoustic design cost in Australia?

There is no published price band for a theatre, because the cost scales with scope: room volume, the isolation the site demands from foyer, street and plant, the complexity of the variable acoustics, and the seat count. A small speech-led theatre is a different project from a large dual-purpose venue, so each is scoped to its own brief.

The entry point is a half-day diagnostic acoustic audit, which runs about $1,500 to $4,000 and grounds a fee proposal in the actual room. From there, a theatre is scoped to its own brief.

Audit fees are quoted ex GST. For a theatre, the economics are buy-once against buy-then-fix: a room that misses its reverberation or intelligibility target after opening costs far more to correct, with the audience already in the seats, than it costs to model and prove before the build.

Who designs and builds theatre acoustics in Australia?

There are two ways to procure theatre acoustics. Consultant-only: an acoustic consultant designs and specifies the room, and a separate builder constructs to that specification. Design and build: one team sets the acoustic targets, builds the room and measures the result, owning the outcome. Most firms work the first way; a smaller set, including AKA Acoustics, design and build.

The difference matters most in a theatre, where the result is judged live and the trade-offs between reverberation, early reflections and isolation are solved on site as the room goes up. In the split model, when the measured result misses, the consultant points at the build quality and the builder points at the specification, and the venue is left with a room that does not perform and a dispute about whose fault it is. Single accountability removes that gap: one team, one contract, one guarantee, no handover from consultant to contractor. AKA adds supply to the model, so the acoustic products specified into the room are the products it sources and stands behind. The full decision, model by model, is covered in our design-and-build versus consultant-only comparison.

AKA's proven base is critical-listening rooms, cinema and post-production theatres. A Sydney Dolby Atmos post-production theatre AKA designed and built inside an existing shell measured NC-20 against an NC-25 requirement, with reverberation of T30 0.17 to 0.20 s across 500 Hz to 8 kHz inside the Dolby calibration band. It was modelled in the Dolby Audio Room Design Tool, its isolation calculated in INSUL, and verified in REW with a log sine sweep spatially averaged over 18 positions, the same critical-listening and measurement discipline a theatre demands. For a theatre brief, talk to our team for an early-stage acoustic review before the design is locked.

How is a theatre proven to meet its acoustic target, and who proves it?

A theatre is proven by measurement, not by adjectives. Reverberation is measured to ISO 3382-1:2009 from the room's impulse response, captured with a log sine sweep and a Class 1 microphone, spatially averaged across seating positions so the result describes the room the audience actually hears. The party that owns design through measurement is the party that proves it.

From that impulse response the standard derives T20 over a decay from minus 5 to minus 25 dB, T30 from minus 5 to minus 35 dB, plus the Early Decay Time. The background-noise floor is proven the same way, against the AS/NZS 2107 dB(A) or NR design target for a performing-arts room, reported in NC where the space is used for critical listening. AKA reports its critical-listening rooms in NC terms, and the working bridge between the AS/NZS 2107 dB(A) target and the NC curve maps a drama theatre's 25 to 30 dB(A) design sound level to roughly NC-25 to NC-30, occupied, at mid-frequency. ISO 9568 is the background-noise method for the cinema and post-production case, where AKA's NC-20 critical-listening result sits.

The discipline is what makes the result defensible. AKA proves it the same way every time: the post-production theatre verified by a spatially-averaged sweep over 18 positions, and a live-music venue where the measured L10 moved only 2.4 dB under a full crowd. In both cases the number was owned by the team that designed and built the room, the party accountable for the design and the build, by measurement, against the criteria set at brief.

Frequently asked questions

What makes a drama theatre acoustically good? Speech intelligibility governs a drama theatre. Every seat needs direct sound reinforced by early reflections inside the first 50 ms, integrating to hold C50 above 0 dB and STI past 0.60, over a noise floor low enough not to mask consonant onsets, with reverberation set to room volume. Four levers set it and they interact: intelligibility and early reflections, a volume-dependent reverberation time, sightline-driven stage-to-audience geometry that holds sound strength G across the seating plane, and isolation from foyer, street and plant. They are solved together against numbers before a wall is built, then verified by measurement to ISO 3382-1.

What reverberation time should a theatre have? There is no single fixed value, because it scales with room volume. AS/NZS 2107:2016 gives auditoria reverberation through volume-dependent guidance, not a single tabled number. A drama theatre of roughly 4,500 to 5,000 cubic metres maps to about 1.1 to 1.2 seconds unoccupied; survey data across drama venues clusters near 1.0 second, and an occupied room runs roughly 0.3 seconds shorter than the same room empty as the audience adds absorption. Speech runs shorter than music, and concert or opera spaces defer to specialist advice rather than a tabled value.

How is speech made intelligible in a theatre? By getting strong, early sound to every seat inside the 50 ms window. The direct sound from the stage reaches the whole audience through a sightline-driven rake and room shape, early reflections off the ceiling, proscenium and side walls reinforce it and raise sound strength G, a controlled reverberation time keeps the decay from masking consonant onsets, and a low noise floor keeps soft passages clear. The intelligibility measures referenced in ISO 3382-1 are a Speech Transmission Index of about 0.6 or better and a C50 above 0 dB for a speech audience.

How do you isolate a theatre from foyer, street and plant rooms? With mass and decoupling: mass-air-mass partitions and structural breaks that raise the field-verified Dn,T,w and L'nT,w, not only the laboratory Rw and Ln,w, to the airborne and impact minimums the National Construction Code enforces at building approval. The weakest path sets the result, and it is rarely the wall: it is the door seal, the airlock, the service penetrations and the flanking transmission around the partition. On a live-music venue, an AKA acoustic door held Rw 48 against an Rw 46 requirement. This isolation axis is separate from the in-room reverberation target, which is the recommended AS/NZS 2107 figure rather than a mandatory minimum.

Can one theatre work for both drama and music? Yes, through variable acoustics. A multipurpose room shifts mid-band reverberation between two regimes a single fixed RT cannot serve: a shorter speech setting led by C50 and STI, and a longer music setting led by EDT, C80 and early lateral energy for reverberance and spaciousness. The tools are retractable absorption such as banners and drapes, adjustable panels presenting an absorptive or reflective face, a coupled volume such as a reverberation chamber, and a demountable orchestra shell. Both settings are modelled before building and measured at commissioning so each one lands, not only the default.

What does theatre acoustic design cost in Australia? There is no published price band, because cost scales with scope: room volume, the isolation demand from foyer, street and plant, the complexity of any variable acoustics, and the seat count. The entry point is a half-day diagnostic acoustic audit at about $1,500 to $4,000, which grounds a fee proposal in the actual room. The economics are buy-once against buy-then-fix: a room that misses its target after opening costs far more to correct than to model and prove first.

How is a theatre proven to meet its acoustic target, and who proves it? By measurement to ISO 3382-1:2009: reverberation from the room impulse response, T20 over minus 5 to minus 25 dB, T30 over minus 5 to minus 35 dB, plus Early Decay Time, captured with a log sine sweep and a Class 1 microphone, spatially averaged across seating positions so the result describes the room the audience hears. The background-noise floor is proven against the AS/NZS 2107 dB(A) or NR design target, reported in NC for critical-listening rooms. The party that owns design through measurement is the party that proves it: the team accountable for the design and the build.

Who designs and builds theatre acoustics in Australia? Most Australian acoustic firms design and specify, then hand construction to a separate builder. A smaller set, including AKA Acoustics, design and build: one team sets the acoustic targets, builds the room and measures the result under a single contract. The difference matters most in a theatre, where reverberation, early reflections and isolation are resolved on site and a split model leaves no one accountable when the room underperforms. AKA's proven base is critical-listening rooms, cinema and post-production theatres, including a Sydney post-production theatre delivered at NC-20.

What standards apply to theatre acoustic design in Australia? AS/NZS 2107:2016 sets the recommended in-room design sound levels and volume-dependent reverberation guidance. The National Construction Code sets the mandatory sound-insulation minimums between spaces, enforced at building approval. ISO 3382-1:2009 is the measurement method for reverberation and the intelligibility measures STI and C50 in performance spaces, while ISO 9568 covers background noise in cinema and post-production rooms. For a theatre pursuing critical-listening or cinema use, Dolby Atmos, THX or IMAX criteria may also apply. A theatre brief usually has to satisfy several of these at once.

Related reading

• Auditorium acoustic design: the complete guide
• Cinema acoustic design: the complete guide
• Home theatre vs media room: the difference, explained