Reverberation Time Targets by Room Type: What to Actually Specify

8 sierpień 2026

Most acoustic enquiries arrive as an area. "I need panels for a 200 square metre hall." It is a reasonable way to ask, but it skips the step that determines whether the room will actually work: deciding what reverberation time you are aiming for. Get the target right and the panel quantity follows from it. Get it wrong and you can install a generous amount of absorption and still end up with a room nobody wants to speak in.

What reverberation time actually is

Reverberation time, written T or RT60, is how long a sound takes to decay by 60 decibels after the source stops. It is measured to EN ISO 3382-2. In practice you will usually see it quoted as Tmf, the mid-frequency average across the 500 Hz, 1 kHz and 2 kHz octave bands, because that is the range speech lives in.

Two things drive it: the volume of the room and the total absorption inside it. Double the volume and reverberation roughly doubles. Add absorption and it falls. This is why a small hard bathroom and a large hard sports hall are both bad but bad in different ways, and why the panel area that fixes a meeting room is nowhere near enough for a gymnasium.

Typical targets by room type

The figures below are the ranges commonly specified across European projects. They are a starting point for scoping, not a substitute for the standard governing your particular building. Always confirm against the regulation that applies, because the numbers move between countries and between new build and refurbishment.

Classrooms: around 0.6 to 0.8 seconds. UK Building Bulletin 93 sets 0.8 seconds or better for new-build teaching spaces and allows a more relaxed figure on refurbishment. Germany works from DIN 18041, which derives the target from room volume rather than fixing a single number.
Open-plan offices: around 0.4 to 0.6 seconds. The goal here is not just decay time but speech privacy, so absorption is only part of the answer.
Meeting rooms and telephone booths: around 0.4 to 0.6 seconds. Small hard rooms routinely measure two or three times this untreated.
Restaurants and bars: around 0.6 to 0.9 seconds. Below this a room can feel oddly dead and lose atmosphere, which is a real commercial consideration.
Sports halls: around 1.5 to 2.0 seconds. This looks generous until you realise an untreated hall of that volume can sit well above 4 seconds.
Swimming halls: around 2.0 seconds. Hard, wet and tall, with the water surface untreatable, so the ceiling carries almost the entire load.
Music rehearsal rooms: around 0.6 to 1.0 seconds, varying with the instrument. A drum room and a choral room want different things.
Corridors and circulation: around 0.8 to 1.2 seconds, mostly to stop noise travelling between spaces.

Where the targets come from

Three documents cover most European work. DIN 18041 is the German standard for acoustic quality in rooms up to moderate volume and is widely referenced beyond Germany. It splits rooms into groups depending on whether communication happens over distance, and derives the target from volume rather than handing you a fixed figure. Building Bulletin 93 is the UK document for school premises and gives explicit figures by space type. National building codes across the Nordics and Baltics carry their own tables, often with a class system that lets a client specify a better-than-minimum result.

Two more standards sit behind the product side. EN ISO 354 is how a panel's absorption is measured in a laboratory reverberation room, and EN ISO 11654 is how that measurement is condensed into the single αw figure and an absorption class from A to E. Our Sonablock panels are tested to both, by RISE Research Institutes of Sweden, reaching αw 0.60 to 0.65 depending on fibre width, which is absorption class C.

Turning a target into a panel quantity

The rough method is Sabine's equation: the absorption you need is proportional to room volume divided by the target time. In practice you do not need to do the arithmetic by hand to scope a job. What you do need is the volume, an honest list of the existing surfaces, and a decision on the target. From there:

Volume, not floor area. A 200 square metre hall with a 3 metre ceiling and the same hall with an 8 metre ceiling are different jobs. Ceiling height is the number people forget to send.
Count what is already absorbing. Carpet, soft seating, curtains, an audience and a stacked storeroom all contribute. A furnished restaurant behaves very differently from the empty shell you measured.
Air gap earns absorption for free. Mounting on battens with a cavity behind, especially with mineral wool in the void, moves absorption down into the low mid frequencies where rooms boom. Our published αw figures assume a 200 mm gap, and fixing tight to a hard wall will not match them.
Distribute, do not cluster. The same panel area spread across ceiling and one or two walls outperforms the same quantity concentrated in a single patch.

Two honest cautions

First, reverberation time is a room-average figure and it hides local problems. A room can hit its target on paper and still have a flutter echo between two parallel hard walls, or a slap back off a glass facade behind a speaker. Fixing those is about placement, not quantity.

Second, absorption is not insulation. Bringing reverberation down inside a room does nothing measurable for the noise passing through the wall to the room next door. That is a matter of mass and separation in the construction, and no panel purchase solves it. It is the most common misunderstanding we deal with, so we would rather say it plainly.