What Is Reverberation Time (RT60) — Explained Simply
Last updated: October 10, 2026
Reviewed by acoustic research sources and WHO guidelines.
When you walk into a cathedral, you notice how sound lingers and swells. In a recording studio, sounds stop almost immediately. The difference is reverberation time — usually expressed as RT60. Understanding it helps you understand why some rooms sound clear and others sound echoey.
Quick Answer: What Is Reverberation Time?
Reverberation time is how long sound lingers in a room after the source stops. It is usually expressed as RT60: the time in seconds for the sound level to drop by 60 dB. A furnished bedroom may have a reverberation time of a fraction of a second; a large stone church can reach several seconds. It gets longer as a room gets larger and harder, and shorter as you add soft, absorbent materials.
Table of Contents
- What Is RT60?
- Echo vs Reverberation
- How RT60 Is Measured
- Typical RT60 Values by Room Type
- What Affects Reverberation Time?
- Practical Examples
- Too Much vs Too Little Reverberation
- How to Estimate Your Room's RT60
- Reducing Reverberation Time
- FAQ
Curious about your room? [Measure your room's noise level with SnapRoomScore](/) — note that it measures sound level, not reverberation time.
What Is RT60?
RT60 stands for Reverberation Time 60. It is the time (in seconds) it takes for sound in a room to decay by 60 decibels after the source stops. A 60 dB drop means the sound energy has fallen to one millionth of its starting value — in practice, from clearly audible to barely perceptible in a quiet room.
- 0.3 seconds: sound dies away quickly; the room sounds "dry"
- around 0.5 seconds: typical of many furnished home rooms
- 1 second or more: noticeable lingering in a home; normal in large halls
- several seconds: large churches and similar spaces
The concept was developed by Wallace Clement Sabine at Harvard in the 1890s. He found that reverberation time depends mainly on:
- Room volume — larger rooms reverberate longer
- Absorption — the total amount of sound-absorbing surface in the room
His formula, the Sabine equation, is still used as a first estimate:
RT60 ≈ 0.161 × V / A
Where V is room volume in cubic metres and A is total absorption in square metre sabins (each surface area multiplied by its absorption coefficient). It works best in rooms with fairly evenly distributed absorption; very absorbent or unusually shaped rooms need other formulas.
Echo vs Reverberation
These terms are often used interchangeably, but they describe different things:
| Echo | Reverberation | |
|---|---|---|
| What you hear | A distinct, separate repetition of a sound | A continuous, blended tail of sound |
| Cause | A strong reflection arriving noticeably later than the direct sound | Many overlapping reflections from all surfaces |
| Typical setting | Large spaces, distant walls, outdoors near cliffs or buildings | Any enclosed room |
| In small rooms | Rare as a true echo; flutter echo (rapid buzzing between parallel bare walls) can occur | Common, especially in empty rooms with hard surfaces |
When people say a small room "echoes", they usually mean it has long reverberation or flutter echo. For practical fixes, see our guide on how to reduce echo in a room.
How RT60 Is Measured
Professional Method
Professional measurements follow the ISO 3382 series of standards:
- Excite the room with an impulse (balloon pop, starter pistol) or a loudspeaker playing interrupted noise or a sine sweep
- Record the decay with a calibrated measurement microphone
- Analyse the decay curve in frequency bands (typically octave bands from 125 Hz to 4 kHz)
- Repeat at several source and microphone positions and average the results
Because a clean 60 dB decay is hard to capture above background noise, the slope is usually measured over 20 or 30 dB (T20 or T30) and extrapolated to 60 dB.
Why Frequency Matters
Reverberation time is usually different at low and high frequencies. Many rooms reverberate longer in the bass, because typical furnishings absorb low frequencies poorly. A single RT60 number is therefore a simplification.
Typical RT60 Values by Room Type
Suitable reverberation depends on the room's size and purpose, and on frequency. The values below are indicative ranges often cited for mid frequencies — not universal targets. Standards and building codes define specific requirements mainly for spaces like classrooms, and those vary by country and room size.
| Room Type | Indicative RT60 | Why |
|---|---|---|
| Recording studio / control room | short, roughly 0.2–0.4s | Controlled, dry sound for accurate listening |
| Bedroom, home office | often around 0.3–0.6s | Furnished small rooms; clear speech on calls |
| Living room | often around 0.4–0.6s | Natural feel for conversation and TV |
| Classroom | typically well under 1s; see local standards | Speech intelligibility |
| Concert hall | roughly 1.5–2.5s | Fullness for orchestral music |
| Large church or cathedral | several seconds | Large volume, hard surfaces |
A small bedroom with a reverberation time well above 1 second would sound noticeably echoey, while a concert hall with 0.3 seconds would sound flat. Context determines whether reverberation is desirable.
For noise levels rather than reverberation, see our guides on normal home noise levels and bedroom noise for sleep.
What Affects Reverberation Time?
Room Volume
Larger rooms reverberate longer because sound travels further between reflections. In Sabine's formula RT60 is proportional to volume divided by absorption. Because a larger room also has more surface area, making a room bigger with the same materials increases RT60, but by less than the increase in volume.
Surface Materials
This is the factor you have the most control over:
- Highly reflective (low absorption): glass, tile, concrete, plaster
- Moderately absorptive: thin carpet, light curtains, some wooden surfaces
- Highly absorptive: thick carpet, heavy curtains, upholstered furniture, porous acoustic panels
Room Shape
Parallel bare walls can create flutter echo. Irregular surfaces, bookshelves and furniture scatter sound and help reflections decay more evenly.
Air Absorption
At high frequencies, air itself absorbs sound energy. This is negligible in small rooms but matters in large halls.
Practical Examples
- An empty, newly painted apartment: hard floor, bare walls, large windows — speech sounds hollow and footsteps ring. Reverberation is long for its size.
- The same apartment after moving in: a sofa, rug, curtains and full bookshelves often make the room sound noticeably calmer, without any acoustic panels. See empty vs furnished room sound.
- A tiled bathroom: small, but almost every surface is reflective, so it sounds lively despite its size.
- A carpeted bedroom with a bed and curtains: short reverberation; voices sound close and clear.
- A large stone church: a very large volume with hard surfaces gives several seconds of reverberation.
Get a baseline of how loud your room is. [Measure your room with SnapRoomScore](/) — instant, free, and no installation required.
Too Much vs Too Little Reverberation
Too Much Reverberation (in a home)
- Speech sounds muddy and unclear
- Video calls pick up a hollow, echoey sound
- Music sounds boomy and unfocused
- Voices and activity build up into a general din
Too Little Reverberation
- The room can feel "dead" or oppressive
- Music can lack warmth
Most furnished homes are closer to the first problem than the second.
How to Estimate Your Room's RT60
The Clap Test
A clap is a rough, subjective check — not a measurement:
- Sound stops almost instantly → the room is well damped
- A short, soft tail → typical of a furnished room
- A clear ringing or buzzing tail → long reverberation or flutter echo worth treating
Using an App
Some acoustic measurement apps estimate RT60 from an impulse. Results depend on the phone's microphone and processing, so treat them as ballpark figures. SnapRoomScore does not measure RT60 — it estimates overall sound level, which is a different quantity.
Reducing Reverberation Time
If your room sounds too echoey, add absorption — roughly from easiest to most involved:
- Add area rugs on hard floors
- Hang heavy curtains on windows or bare walls
- Add upholstered furniture and cushions
- Fill bookshelves — they break up reflections
- Install acoustic panels at reflection points
- Add bass traps in corners for low-frequency buildup
- Treat the ceiling with panels or clouds in larger rooms
Reducing reverberation does not soundproof a room — it does not stop sound entering from outside. For practical improvements, read how to fix room echo and improving acoustics without expensive panels.
Start by understanding your space. [Measure your room's noise level now with SnapRoomScore](/) — it takes seconds.
FAQ
What is reverberation time?
Reverberation time is how long sound keeps lingering in a room after the source stops. It is usually given as RT60: the time in seconds for the sound level to fall by 60 dB. Larger rooms and hard, reflective surfaces give longer reverberation times; soft, absorbent materials shorten them.
What is the difference between echo and reverberation?
An echo is a distinct, separately audible repetition of a sound, typically from a distant reflecting surface. Reverberation is the dense blend of many reflections that merge into a continuous tail. Small rooms rarely have true echoes, but they can have noticeable reverberation or flutter echo between parallel walls.
What is a good RT60 for a living room?
There is no single ideal value. Ordinary furnished living rooms often have reverberation times somewhere around half a second; values well above that tend to sound echoey. Suitable values depend on room size, use and frequency, and standards define targets mainly for specific spaces such as classrooms.
How is RT60 measured?
Professionally, reverberation time is measured according to ISO 3382 using a calibrated microphone and either an impulse (such as a balloon pop) or an interrupted noise or sine sweep. The decay is analysed in frequency bands, usually over a 20 or 30 dB range (T20 or T30) and extrapolated to 60 dB, at several positions in the room.
Can SnapRoomScore measure RT60?
No. SnapRoomScore estimates the overall sound level from your microphone; it does not analyse decay curves and cannot measure reverberation time. Dedicated acoustic apps can give a rough RT60 estimate, and professional measurement requires calibrated equipment.
