Room acoustics
Reverberation Time for Churches
Quick answer
Aim for 1.0 to 1.4 seconds of RT60 for a blended service, 0.8 to 1.2 for a contemporary band, 0.6 to 0.9 for speech only and 1.6 to 2.4 for choir and organ. A hard-surfaced 250 seat sanctuary typically measures about 2.5 seconds, a full second too long for a band.
Reverberation time is the single number that decides whether a sanctuary is easy or impossible to mix in. It is the time taken for sound to decay by 60 decibels after the source stops, written RT60, and it is set by the volume of the room and the absorption of its surfaces. Nothing in a rack changes it.
The reason it matters so much to churches is that the right answer depends entirely on what happens in the room. A cathedral at 2.4 seconds is glorious for a choir and unusable for a drummer. A carpeted multipurpose room at 0.6 seconds is perfect for teaching and makes congregational singing feel thin and exposed. Most church conflicts about sound are really disagreements about this number. Estimate yours with the acoustic treatment calculator, then read what to do about it in acoustic treatment for a sanctuary.
On this page
What should your room measure?
These targets are mid-frequency figures, typically averaged over the 500 Hz and 1 kHz octave bands, measured with the room empty. A congregation shortens the measured time, which is one reason the empty-room figure is the one used for design.
A contemporary worship band wants 0.8 to 1.2 seconds, while a choir and organ room wants 1.6 to 2.4 seconds, a difference of a full second in the same building.
| Dominant use | Target RT60 | What it sounds like | What goes wrong outside it |
|---|---|---|---|
| Speech and teaching | 0.6 to 0.9 s | Crisp, close, every consonant | Longer and teaching gets mushy at the back |
| Contemporary worship band | 0.8 to 1.2 s | Tight low end, controlled cymbals | Longer and the drums smear into everything |
| Blended, piano and small band | 1.0 to 1.4 s | Supportive without washing | The widest usable compromise |
| Choir, organ and hymns | 1.6 to 2.4 s | Blended, sustained, the room sings | Shorter and the choir sounds thin and exposed |
Figures are the mid-frequency target for the empty room. Rooms rarely sit at one value across the spectrum: a carpeted room with hard walls is often short above 1 kHz and long below 250 Hz, which measures acceptably and still sounds boomy.
What an untreated sanctuary really measures
Sabine's equation in imperial form is RT60 equal to 0.049 times the volume in cubic feet, divided by the surface area times the average absorption coefficient. Average absorption for a hard-surfaced room with painted drywall or plaster, a tile or wood floor and wooden pews is around 0.08. Carpet, padded pews and an acoustic tile ceiling push it toward 0.15 to 0.20.
A hard-surfaced 250 seat sanctuary at an average absorption of 0.08 measures about 2.47 seconds, twice the blended-service target.
| Room | Volume | Surface | a = 0.08 hard | a = 0.12 mixed | a = 0.15 carpeted | a = 0.20 treated |
|---|---|---|---|---|---|---|
| 100 seats | 10,240 cu ft | 3,466 sq ft | 1.81 s | 1.21 s | 0.97 s | 0.72 s |
| 250 seats | 28,500 cu ft | 7,054 sq ft | 2.47 s | 1.65 s | 1.32 s | 0.99 s |
| 500 seats | 69,000 cu ft | 13,250 sq ft | 3.19 s | 2.13 s | 1.70 s | 1.28 s |
| 1,000 seats | 151,200 cu ft | 23,052 sq ft | 4.02 s | 2.68 s | 2.14 s | 1.61 s |
Volumes come from the standard sanctuary model used across this site: about 7.5 square feet per seat and a ceiling that rises with the span. Sabine over-states RT60 in very absorptive rooms, so the right-hand column is optimistic by perhaps 10 percent in practice.
The pattern churches keep hitting
Read down the 0.08 column and the problem announces itself. Reverberation time grows with volume faster than it grows with surface area, so a bigger sanctuary is always a more reverberant sanctuary at the same construction. A 100 seat hard room at 1.81 seconds is a nuisance. The same construction at 1,000 seats measures 4.02 seconds, which is a cathedral, and a worship band in it is simply not going to work without treatment.
This is also why the same denomination's 250 seat chapel and 1,000 seat sanctuary need different service styles to sound right, and why a church that grows into a larger building often finds its sound problems get worse rather than better after spending more money on equipment. The building changed, and the building is the dominant variable. Check the figures for your own seat count on the sanctuary size pages.
How to measure your own room
- Clear the room and stop the air handling. Measure with the room empty and the HVAC off. Background noise raises the floor of the measurement and air movement changes the result. Note the temperature, because it is worth recording alongside the figure.
- Make a loud, short, broadband sound. A single sharp hand clap, a balloon burst or a starter-pistol style impulse works. Stand near the platform, roughly where a preacher stands, and let the sound decay fully before the next one.
- Record it from three positions. Capture the decay from the front third, the middle and the back of the seating with a phone RT60 app or a laptop with a measurement microphone. Rooms are not uniform, and three readings tell you whether you have one problem or several.
- Read the mid-band figure. Take the 500 Hz and 1 kHz bands and average them. That is the number compared against the targets. If the app reports only a single broadband figure it will be dominated by the low end and will read longer than the mid-band truth.
- Compare against your service style. Subtract your target from your measurement. That gap is what treatment has to close, and the panel count comes straight from it. A 250 seat room measuring 2.2 seconds against a 1.2 second target needs about 78 panels.
- Repeat after any building change. New carpet, replaced seating, a removed wall or a new ceiling all move the figure. Re-measure and then retune the system, because any tuning done before the change no longer matches the room.
Why one number is not the whole story
RT60 is an average, and two rooms with the same average can sound completely different. A room that is short above 1 kHz because of carpet and long below 250 Hz because the walls are hard measures acceptably and still booms. A room with one strong flutter echo between two parallel hard walls can have a perfectly reasonable RT60 and an obvious slap that ruins speech.
So measure by octave band where you can, and use your ears for the things the number hides: a distinct slap when you clap, a single bass note that rings when the band plays, a rear wall echo audible from the platform. Those are specific defects with specific fixes, and they are usually cheaper to solve than a whole-room reduction.
The other thing the number hides is noise. A sanctuary with a 0.9 second decay and an air handler running at 45 dBA has a signal-to-noise problem, not a reverberation problem, and the system will be turned up to overcome it. Measure the background noise while you are in there with a meter.
Living with a room you cannot change
Plenty of churches have a historic sanctuary where treatment is not permitted, or a leased space where it is not possible. The strategy then is to stop asking the room to help and to deliver more direct sound relative to reverberant sound. That means tighter loudspeaker patterns aimed only at seats, more sources closer to the listeners, and the discipline of never turning the system up to fight the room.
In practice that is a narrower box, often 60 by 40 degrees rather than 90 by 50, aimed as described in how to aim and place church speakers, plus delay fills for the deep seats as covered in under-balcony delay speakers. A column array such as QSC KC12-BK System Column Line Array PA is popular in reverberant historic rooms for exactly this reason: its narrow vertical pattern puts energy on the congregation rather than on the ceiling and the upper walls.
The service style is a lever too, and it is a leadership conversation rather than a technical one. A room at 2.4 seconds is telling you what it was built for. Also worth doing: reduce acoustic stage volume, because in a live room every decibel from the platform is multiplied by the building. That is the argument in reducing stage volume in church.
Sources
- Sabine reverberation equation and RT60 targets as implemented in src/lib/avmath.mjs
- Published absorption coefficients for common church building materials
Frequently asked questions
What is a good RT60 for a church?
It depends on what happens in the room, and that is not a dodge. Speech and teaching want 0.6 to 0.9 seconds, a contemporary band wants 0.8 to 1.2, a blended service 1.0 to 1.4, and choir and organ 1.6 to 2.4. A room serving several styles is a compromise, and the usual landing point is the blended range because it is the only band that overlaps most of the others.
How do I measure reverberation time without professional equipment?
A phone app and a hand clap gets you within a few tenths of a second, which is enough to plan treatment. Empty the room, switch off the air handling, clap sharply near the platform and capture the decay from three seating positions. Read the 500 Hz and 1 kHz bands and average them. A broadband single number reads long because the low end dominates.
Does a full congregation change the reverberation time?
Substantially. People are effective absorbers above about 250 Hz, and a congregation of 250 adds several hundred sabins, which can cut a couple of tenths off the measured decay. Design and measure with the room empty, because that is the worst case and the one a wedding or a midweek meeting will actually experience.
Why does a bigger sanctuary sound more reverberant?
Because reverberation time scales with volume divided by absorption, and volume grows faster than surface area as a room gets bigger. The same construction that measures 1.81 seconds at 100 seats measures 4.02 seconds at 1,000 seats. That is why a church that grows into a larger building often finds its sound problems get worse even after spending far more on equipment.
Can equalisation fix a reverberant room?
No. Reverberation is energy arriving late, and an equaliser changes level by frequency, not by time. Cutting the frequencies that ring makes the system quieter in that range without making the decay shorter, and it costs you the same frequencies in the direct sound that carries the words. The fixes are absorption, tighter coverage patterns and lower stage volume.
Is a long reverberation time always bad?
Not at all. A choir, an organ and congregational singing all depend on it, which is exactly why historic churches were built the way they were. A 2.0 second room makes a hymn sound magnificent and a kick drum sound like a landslide. The problem is never the room on its own, it is the mismatch between the room and what the church asks it to do.
Researched, not professional advice. This page is compiled from published manufacturer specifications, operator manuals, FCC rules, published standards and owner-review consensus, not hands-on testing. Sound system design, rigging loudspeakers overhead, and any electrical work are jobs for a qualified professional: have flown loudspeakers and their attachment points signed off by a structural engineer or a certified rigger, and have all wiring done by a licensed electrician to your local code. Wireless microphone rules change, so confirm the current FCC position before buying. As an Amazon Associate we earn from qualifying purchases.