RT60 Acoustic Calculator.
Room dimensions and finish materials in, indicative RT60 reverberation time and recommended absorber area out. Sabine equation; defensible for early-stage acoustic planning.
- Boardroom target
- 0.4–0.6 s
- Cinema target
- 0.3–0.4 s
- Mastering
- 0.2–0.3 s
- Standard
- ISO 3382
— Acoustic · RT60 · Sabine · ISO 3382
The room's reverberation time.
Sabine equation (RT60 = 0.161 × V / A) with 1 kHz absorption coefficients — a single-band brief-stage estimator per ISO 3382. Production design always runs octave-band (125 Hz – 4 kHz) and validates on-site with calibration microphone impulse measurement.
Premium consultation · Office / classroom
0.67 s RT60
Within target — the office / classroom band sits at 0.50–0.70 s. Total absorption is 34.6 Sabins across 144 m³.
Room volume
144 m³
Office / classroom
Calculated RT60
0.67 s
Within target
Total absorption
34.6 Sabins
Σ surface × coefficient
Target band
0.50 – 0.70 s
for this volume
Recommended absorber treatment
≈ 3–6 m²
Indicative range · 50 mm fabric-wrapped panel, distributed across walls + ceiling — confirm the quantity with octave-band modelling
Assumptions driving this recommendation↓ expand
- Floor
- Carpet (heavy) (α = 0.5)
- Walls
- Painted drywall (α = 0.08)
- Ceiling
- Painted drywall (α = 0.08)
- Method
- Sabine equation, 1 kHz single-band
- Measurement standard
- ISO 3382 brief-stage estimator
- Production model
- Octave-band 125 Hz – 4 kHz · EASE / Treble
- Panel α
- 0.85 (premium 50 mm fabric-wrapped)
- Cinema target tolerance
- ± 0.05 s (SMPTE / Dolby Atmos)
Operationally sensible ecosystem
Brands grouped by engineering role — not random logos.
Loudspeakers
LCR / surround / overhead arrays
- KEF ReferenceAudiophile-grade home cinema
- JBL SynthesisPro-cinema lineage for residential
- Sonance ReferenceArchitectural reference series
Amplification
Multi-channel + multi-room
- Crown DCi NetworkTouring-grade install amp
- Lab.gruppen ECompact multi-channel install
AV distribution
Matrix + AV-over-IP + endpoints
- Crestron DM NVXAV-over-IP 4K60
- Crestron DM 8K8K HDBaseT matrix
Sabine model is a first-order estimator per ISO 3382 — a single 1 kHz coefficient does not capture low-frequency modal behaviour or high-frequency air absorption. Production design always runs octave-band (125 Hz – 4 kHz) modelling in EASE / Treble and validates on-site with a calibration microphone + impulse measurement before committing specification. Cinema / mastering rooms target ± 0.05 s tolerance per SMPTE and Dolby Atmos certification.
Translate into a briefNext step
Take this acoustic target to the AV desk.
This Sabine estimate is an indicative planning figure, not a final design. A short brief lets us run octave-band modelling and validate on-site with an impulse measurement.
· Engineering advisory · RT60 Acoustic Calculator
What the RT60 number predicts about the room's behaviour.
The RT60 figure is the brief-stage acoustic envelope. The deployment requires the absorber placement geometry, the per-frequency band check and the integration with the PA / DSP profile below.
Deployment observations
- Sabine's RT60 assumes a diffuse-field acoustic — accurate for rectangular rooms with mixed finishes; biased toward higher RT60 in highly absorptive rooms (over-prediction) and biased toward lower RT60 in highly reflective rooms (under-prediction). The number is a design-stage anchor, not a measurement-stage verdict.
- Mid-band RT60 (500 Hz / 1 kHz) is what Sabine predicts well; bass response (below 200 Hz) is governed by modal behaviour and requires separate modal analysis or measurement. Cinema and mastering rooms always need a measured RT60 with calibrated equipment.
- Absorber area is the answer; absorber placement is the engineering. Panel-and-cloud treatment with calculated coverage and material discrimination outperforms uniform-density treatment by 0.1-0.2 RT60 seconds at the same panel area.
Environmental considerations
- HVAC noise is the leading silent acoustic floor — a designed RT60 of 0.5 s in a room with NC-45 HVAC sounds as poor as RT60 of 1.0 s in a NC-30 room. The PA design's STI is bounded by both RT60 and the HVAC noise floor.
- Humidity affects absorber performance — porous absorbers lose efficiency at high humidity (above 75% RH); the design RT60 holds in air-conditioned rooms but drifts in non-AC venues across monsoon-to-dry seasons.
- Audience occupancy is itself acoustic absorption — RT60 measured empty is 20-40% higher than RT60 measured at full occupancy. The design target is the occupied RT60, not the empty-room measurement.
Commissioning discipline
- Measured RT60 with calibrated equipment at commissioning — per AES-15id for performance venues, per ISO 3382-1 for room acoustic measurement. The measurement report sits in the handover pack against the design target.
- Per-frequency-band measurement at 125, 250, 500, 1k, 2k, 4k, 8k Hz — uniform RT60 across the band is rare; the band-wise variation is what informs the absorber-and-diffuser placement, not the single mid-band figure.
- STI measurement at every seat — the PA / DSP profile is set against the measured RT60 and the measured noise floor, not the design-stage assumption.
Lifecycle implications
- Absorber materials carry a 12-15 year service envelope — fabric panel re-fabric is the leading maintenance signal; the panel substrate and the absorber core hold longer than the fabric face.
- Room geometry changes (lighting fixture additions, ceiling treatment changes, audience-chair upholstery refresh) all shift the RT60 — any room-acoustic change triggers a re-measurement on the AMC schedule.
Expansion readiness
- Adding capacity (extra seats, gallery extensions) shifts the RT60 — typically downward as the seat count adds absorption; the PA / DSP profile is re-tuned against the new RT60 measurement, not assumed unchanged.
· Why it matters
A boardroom with a 0.45 RT60 sounds clear in person and on the conference call. The same room at 0.9 — bare drywall, glass tables, hard ceiling — turns every voice into a smear and every video meeting into a request to repeat. RT60 is the single number that separates one from the other, and it is decided by absorber area before drywall ever goes up.
· Frequently asked
RT60 —
what people ask first.
What is RT60 and why 60 decibels?
RT60 is the time, in seconds, for a sound to decay by sixty decibels — roughly the drop from a normal voice to inaudible. It is the standard measure of reverberation across acoustic engineering, ISO 3382 and most cinema and broadcast specifications.
What inputs do I need?
Room length, width and height, plus the dominant finish materials on floor, walls and ceiling. The calculator uses Sabine absorption coefficients and gives a single mid-band RT60 — accurate enough for the first design conversation.
Is the Sabine equation accurate enough for cinemas?
For early-stage planning, yes. Sabine assumes a diffuse field, which holds well for rectangular rooms with mixed finishes. Reference cinemas, mastering rooms and recording spaces still need a measured RT60 with calibrated equipment, plus modal analysis below 200 Hz.
What RT60 should I target?
Boardrooms and conference rooms: 0.4 to 0.6 seconds. Home cinema: 0.3 to 0.4. Recording or mastering: 0.2 to 0.3. Lecture halls and worship halls: 0.8 to 1.2 depending on volume. The tool flags the band for your selected room type.
Will you size and supply the absorbers?
Yes. We design and install acoustic treatment as part of cinema, boardroom and listening-room projects — fabric-wrapped panels, diffusers and bass traps, sourced from European manufacturers and tuned on site after install.
· Begin
Treating a room
that has to sound right?
Send the room dimensions, intended use and any acoustic measurements you already have. We will write back with a treatment plan within two working days.