Think about a film being made. The director does not simply walk onto a set and start shooting. There is a screenplay to develop, a budget to secure, locations to scout, a cast to assemble, a shot list to plan, a production schedule to coordinate, and a post-production pipeline to run — all before the final film reaches a cinema. Each stage builds on the one before it. Skip the screenplay and the shoot collapses. Rush the post-production and the final cut is unwatchable.
Acoustic design follows the same staged logic. An acoustic consultant who parachutes in during construction to discover that the mechanical plant room is directly above the executive boardroom — connected by an unlined concrete slab — cannot fix the problem without major structural work. Acoustic design done properly is a systematic process that starts with the brief, runs parallel to the building design through all its stages, and ends not when the building opens, but when the acoustic performance has been measured and verified.
This guide walks through all eight stages of that process.
Stage 0: Strategic Definition — Is Acoustics a Project Risk?
Before any design work begins, the project team should assess whether acoustic performance is a critical risk factor. Some project types have low acoustic complexity: a suburban warehouse, a single-occupancy villa in a quiet rural setting, a simple office refurbishment in a low-noise location. Others carry significant acoustic risk from the outset: a school adjacent to a railway line, a recording studio in a city centre, a hospital above an underground car park.
At Stage 0, the acoustic consultant (or the architect acting in that capacity) should review:
- Site noise environment: Is the site affected by road traffic, rail, aircraft, industrial processes, or entertainment venues? If external noise exceeds approximately 55 dB(A) during daytime and 45 dB(A) at night, acoustic mitigation will be needed in the building envelope.
- Internal adjacencies: Will the building contain noise-sensitive spaces (recording studios, bedrooms, examination rooms) adjacent to noise-generating spaces (plant rooms, gymnasiums, kitchens, loading docks)?
- Applicable standards: Which acoustic standards apply by regulation or client requirement? BB93 for schools? WELL v2 for certified office interiors? ISO 3382-1 for a performance space?
- Project programme: Is there enough time in the programme to conduct pre-design site noise surveys (which require measurement over multiple 24-hour periods)?
Stage 1: Preparation and Briefing — Setting the Acoustic Brief
Stage 1 (RIBA Stage 1: Preparation and Briefing) is when the acoustic performance requirements are formally established. The acoustic brief produced at this stage is the most important document in the entire process — it defines what "success" looks like.
A complete acoustic brief specifies, for each major space type in the building:
- RT60 target range: e.g., "Open-plan office: 0.4–0.6 s at 500 Hz and 1000 Hz, per ISO 3382-2"
- Background noise criterion: e.g., "NR 35" or "NCB-35" or "≤ 35 dB(A)" depending on the standard used
- Airborne sound insulation: e.g., "DnT,w ≥ 43 dB between adjacent bedrooms, per BS EN ISO 16283-1"
- Impact sound insulation: e.g., "L'nT,w ≤ 58 dB between floors, per BS EN ISO 16283-2"
- Speech intelligibility: e.g., "STI ≥ 0.60 in all seating positions of the lecture theatre"
- Special requirements: Masking system targets for open-plan offices, vibration criteria near precision equipment, noise rating for external facade
Stage 2: Concept Design — Acoustic Zoning and Initial Simulation
Stage 2 is where the architect develops the first spatial arrangement of the building. This is the most influential acoustic stage for large, complex buildings.
The acoustic consultant's role at Stage 2 includes:
Acoustic zoning: Grouping spaces by acoustic sensitivity and segregating noisy zones from quiet zones. The fundamental rule is that quiet spaces should not share walls, floors, or ceilings with noisy spaces. If a recording studio must be adjacent to a mechanical plant room, the design must provide either separation space (a dedicated acoustic buffer zone, such as a corridor or store) or a heavily isolated structural assembly.
Preliminary RT60 calculations: Using Sabine's formula or the Eyring formula, the consultant estimates RT60 for key rooms based on the proposed room volumes and indicative surface materials. At Stage 2, surface areas are known but materials are not yet specified, so calculations use indicative values (e.g., "assume suspended mineral-fibre ceiling and medium carpet").
Initial simulation: For complex performance spaces — concert halls, lecture theatres, auditoria — the consultant may build a simplified geometrical acoustic model at Stage 2. Software tools (and online tools like AcousPlan) allow room geometry to be modelled and absorption distributions to be tested before any material selections are confirmed. The goal at Stage 2 is not precision but direction: is the volume appropriate for the target RT60? Is there a risk of flutter echo between the proposed parallel side walls? Does the proposed ceiling height create useful early reflections to the rear stalls?
Critical feedback: The acoustic consultant provides feedback on the Stage 2 design identifying elements that should be changed before the design is developed further. Common Stage 2 findings include: plant room location that would require extraordinarily high insulation to achieve noise targets; a lecture theatre volume so large that the RT60 target would require excessive absorption; parallel wall pairs that create flutter echo risk.
Stage 3: Developed Design — Material Selection and Detailed Calculations
At Stage 3, the design is developed in sufficient detail to allow quantitative acoustic calculations rather than estimates.
The acoustic consultant produces:
Detailed RT60 calculations by octave band: Using the measured absorption coefficients of specified materials at 125 Hz, 250 Hz, 500 Hz, 1000 Hz, 2000 Hz, and 4000 Hz. At this stage, the calculations should match the agreed acoustic brief criteria within ±0.1 s. If they do not, material substitutions or coverage changes are proposed.
Sound insulation predictions: Using empirical mass-law calculations and published test data for the specified wall, floor, and ceiling assemblies. The relevant standard for European projects is ISO 15712-1:2005, which provides a method for predicting flanking transmission in addition to direct transmission through the separating element.
Background noise assessment: Using the mechanical engineer's equipment data (fan power, duct sizes, diffuser selections) and the proposed duct lining specifications, the acoustic consultant calculates the predicted noise levels in each space and checks them against the brief criteria.
Vibration assessment (if required): For buildings with sensitive equipment or performance spaces, the consultant assesses ground-borne and structure-borne vibration from external sources (railways, road traffic) and internal sources (plant, lifts).
The Stage 3 report documents all calculations and clearly identifies any spaces where the design does not yet achieve the brief. Design changes at Stage 3 are relatively straightforward — material substitutions, additional duct lining, revised plant room layout. They become progressively more expensive at later stages.
Stage 4: Technical Design — Specification Writing
Stage 4 converts the acoustic design intent into contractor-enforceable technical specifications. The output is typically:
- Acoustic performance specifications for each element type (e.g., "Partition Type AP-1: minimum Rw + Ctr = 50 dB, tested per ISO 717-1")
- Schedules of acoustic materials with specified performance values
- Annotations on drawings indicating acoustic treatment locations, ceiling tile types, and critical construction details
- Duct lining specifications and plant room structural isolation details
Stage 5: Manufacturing and Construction — Inspections and RFIs
During Stage 5, the acoustic consultant's role shifts from design to oversight. Regular site inspections are essential because acoustic performance is highly sensitive to construction quality: a single unsealed penetration through a separating wall can reduce its sound insulation by 10 dB or more.
Key inspection points include:
- Sealing and perimeter detailing: All penetrations through acoustic separating elements (pipes, conduits, cables, light fittings) sealed with acoustic mastic or mineral wool packing.
- Floating floor isolation: Resilient bearings installed without bridging; screed poured without contact with walls (perimeter gap maintained).
- Acoustic ceiling tile installation: Tiles cut accurately, no gaps at perimeters, acoustic barriers above the ceiling void in designated locations.
- Duct lining installation: Correct liner thickness, lining continuous without gaps, no compression of liner at bends.
- Door and window seals: Acoustic seals compressed at perimeter, door closers set to ensure full closure.
Stage 6: Handover and Close-Out — Performance Testing
Before handover, the acoustic consultant conducts field measurements to verify that the completed building achieves the specified performance. Unlike laboratory measurements (conducted under controlled conditions), field measurements capture real-world construction quality including flanking paths and installation defects.
Standard test protocols include:
- RT60 measurement: Per ISO 3382-2:2008 using calibrated dodecahedron loudspeaker and precision sound level meter with automated T20/T30 analysis. Minimum 6 source-receiver positions per room.
- Airborne sound insulation: Per ISO 16283-1:2014, reporting DnT,w (field measurement with the flanking correction) compared to specification.
- Background noise: Per BS 8233:2014 or equivalent, with building services running at normal operating mode.
- The cause is investigated (construction defect, material substitution, design miscalculation)
- Responsibility is determined (design issue vs. contractor defect)
- Remedial options are assessed and costed
- Agreed remediation is implemented and retested
Stage 7: In Use — Post-Occupancy Evaluation
The final stage is post-occupancy evaluation (POE), typically conducted 6–12 months after the building has been occupied. User surveys, combined with acoustic re-measurement, identify any performance issues that emerge under real occupancy conditions.
Common findings include: RT60 higher than predicted because occupants have removed or repositioned furniture; background noise higher than specified because HVAC systems are being run at higher flow rates than the design assumed; speech privacy complaints in open-plan offices despite meeting the specified RT60.
POE findings close the feedback loop for the acoustic consultant's practice and generate evidence for improving future projects.
How AcousPlan Helps Across the Process
AcousPlan's simulation engine supports acoustic design from Stage 1 through Stage 6:
- Stage 1–2: Rapid RT60 estimation from room volume and indicative material selections, helping set realistic brief targets and test preliminary layouts
- Stage 3: Detailed octave-band calculations using published absorption coefficients from 5,000+ materials in the database
- Stage 4: Material specifications with manufacturer data, automatically formatted for inclusion in schedules
- Stage 6: Comparison of measured vs. predicted RT60 curves to identify discrepancies and support defect diagnosis