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Specification guide

RT60 and Reverberation Explained

Why a tiled bathroom echoes and a curtained bedroom doesn't — the single number that describes how long sound lingers in a room, why it makes restaurants exhausting and meetings unintelligible, and how it's tuned.

Clap once in an empty tiled bathroom and the sound rings on for a moment; do the same in a curtained bedroom and it dies instantly. That lingering is reverberation, and the number that measures it is RT60. It has nothing to do with blocking sound between rooms — it’s entirely about how a room sounds inside — but it decides whether a restaurant is pleasant, a meeting intelligible, a classroom teachable and a studio usable. This guide explains it plainly.

What RT60 Actually Measures

RT60 is the time, in seconds, for a sound to fade by 60 decibels after the source stops — in effect, how long the echo hangs in the air before it’s gone. A long RT60 means an echoey, “live” room where sounds pile on top of each other; a short RT60 means a “dead,” controlled room where each sound stops cleanly. It is governed by two things: the room’s size (bigger rooms reverberate longer) and how absorbent its surfaces are (hard surfaces reflect, soft surfaces absorb). It is the room-scale expression of the NRC absorption rating covered in STC, IIC and NRC Explained.

Why Reverberation Ruins Rooms

Reverberation is the hidden culprit behind a surprising range of everyday complaints.

  • Restaurants and cafés — hard, fashionable surfaces (concrete, glass, tile) push RT60 up until every table’s conversation smears into a wall of din. Diners raise their voices, which raises the noise floor further, in a feedback loop. Surveys suggest most diners actively avoid restaurants they find too loud — reverberation, not the music, is usually the cause.
  • Meeting rooms and classrooms — high RT60 blurs consonants, so speech becomes hard to follow. On a video call it’s worse still: the microphone picks up the echo and the person at the other end hears a hollow, tiring voice.
  • Open-plan offices — long reverberation spreads every conversation across the floor, which is exactly what wrecks concentration.
  • Worship spaces and halls — a beautiful, resonant church can be gloriously musical yet leave the sermon unintelligible; the art is balancing the two.

In every case the problem is not that the room is loud to the neighbours — it’s that the room is punishing to be in. That’s a treatment problem, not a soundproofing one.

What Good RT60 Looks Like

There is no single “correct” RT60 — the right target depends on the room’s purpose:

  • Recording / critical listening studios — roughly 0.2–0.4 seconds: very controlled, so the room adds as little of its own character as possible.
  • Meeting rooms, offices, classrooms — around 0.6–0.8 seconds: clear speech without feeling clinical.
  • Restaurants — kept short enough that neighbouring tables don’t merge, typically well under a second.
  • Concert halls and worship music spaces — deliberately longer, often 1.5–2 seconds, to give music warmth and bloom.

Matching the target to the use is the whole craft. Too long and speech is muddy; too short and the room feels oppressive and unnatural — which is why absorption is balanced with a little diffusion, explained in Absorption, Blocking and Diffusion.

How RT60 Is Tuned

Because RT60 is driven by absorption, you tune it by adding or removing absorptive area. In practice that means acoustic panels on walls, baffles or “clouds” hung from ceilings, and soft furnishings — sized and placed to bring the measured RT60 to the target for that room. We measure the room first, calculate how much absorption a given target needs, and install to hit it, then re-measure to confirm. This is the substance of our acoustic treatment and echo control, and it’s what a restaurant, office or commercial venue fit-out usually needs. In humid coastal Ghana the panels should be mineral wool or PET rather than open-cell foam, which absorbs moisture and fosters mould above 60–70% relative humidity.

RT60 Is Not Soundproofing

The single most important thing to understand: tuning RT60 makes a room sound better inside — it does not stop sound reaching the next room. Absorbing echo and blocking transmission are opposite jobs, and confusing them is the most common and costly mistake in the field. A restaurant with perfect RT60 can still leak into the flat above; a bedroom can be blocked to a high STC yet still echo unpleasantly. Many rooms need both. We untangle this fully in Soundproofing vs Acoustic Treatment and set the whole context in How Soundproofing Actually Works.

Is your space echoey, exhausting or hard to hear in? Book a free noise assessment: +233 20 531 3333.