Room Reverb RT60 Test: Measure Reverberation Time
Overview
Room Reverb RT60 Test. Click Play Burst & Measure and the Room Reverb RT60 Test uses your microphone to capture a short noise burst plus its decay across your room, then works out a reverberation time range and a plain-language verdict on whether your space sounds clear or echoey on calls. There's nothing to type in here — just allow microphone access, keep the room quiet, and let the burst do the rest. Watch the spectrum analyzer update in real time as you test.
A room reverb RT60 test tells you how long sound lingers after a clap, a balloon pop or a stopped speaker, and that single number shapes speech intelligibility and listening clarity in any room. Below you will see how reverberation time is measured, calculated, judged and fixed, with sound energy fading by exactly 60 dB as the yardstick.
What Is RT60 Reverberation Time in Room Acoustics?
When a sound stops, the sound pressure level does not drop to silence at once. Waves keep bouncing off hard surfaces and reflective surfaces such as glass, drywall and bare floors until their energy runs out. That lingering wash is reverberation, and RT60 (also written T60) is the time, in seconds, it takes the level to fall by 60 dB. People also call it reverb time or decay time, and it is the basic number in room acoustics because it predicts how your hearing experiences a space. The subwoofer kick test tool gives you a clear answer instead of guessing.
Reverberation is different from an echo. An echo is one distinct reflection, while reverberation is the dense sound decay built from thousands of reflections.
Why 60 dB Is the Benchmark
The loudest passages of an orchestra reach roughly 100 dB, while a quiet background level sits near 40 dB. A 60 dB drop therefore describes the loudest sound fading into the background, which is why a concert hall is judged by it. In practice the decay is rarely measured over its full dynamic range, as the shortcuts below show.
How a Room Reverb RT60 Test Works
Every RT60 measurement follows one idea: energise the room, stop the source, and record how the level falls. To measure RT60 you need a loud, abrupt source, a microphone or mic, and software that plots the decay. A phone app, a dedicated RT60 app, or free tools such as Room EQ Wizard can do the plotting, but the maths is the same. Run the test at several positions and keep the audio level well above the room's noise. The dynamic range listening test runs entirely in your browser via the Web Audio API — nothing is uploaded anywhere.
Sound Level Meter and Microphone Setup
A sound level meter with room acoustics firmware is the professional choice, though a calibrated measurement microphone works too. Place it at ear height, away from walls, and check that the background noise is at least 35 dB below your peak. Measure the background level first, in silence, so you know how much usable range the decay has.
Interrupted Noise and Impulse Response RT60 Methods
The interrupted noise method plays steady pink noise, then cuts it and records the fall. The impulse response method uses a single burst, such as a pop or a swept sine, and calculates the decay mathematically. A sweep signal gives the cleanest result across every hz band, and in both cases you measure reverberation time from the recorded curve.
Reading an RT60 Decay Curve
The decay curve plots level against time. A straight, steep slope means a short, even decay; a slope that bends or flattens shows noise or a second resonance. A spectrogram adds frequency, and the usable dynamic range ends where the curve meets the noise floor.
Choosing a Sound Source for Measuring Reverberation Time
The best sound source is loud, abrupt and omnidirectional, so it excites the whole room equally. Your choice depends mostly on room size:
- Dodecahedron speaker: the professional standard for small to large rooms, with an even output in every direction.
- Portable loudspeaker: a cheaper option playing pink noise, though you may need several speaker positions.
- PA system: practical in concert halls and other large spaces.
- Balloon pop: free, nearly omnidirectional and excellent for homes; a bigger balloon carries more bass.
- Starter pistol: loud and fast, but unsuitable in public buildings.
- Clapperboard or hand clap: a quick estimate only, since a clap lacks low-frequency energy.
Calculating RT60 With the Sabine Formula
Wallace Sabine showed that the decay depends on the volume of the room and its total absorption in sabins. The Sabine formula in metric units is:
$$RT_{60} = \frac{0.161 \times V}{A}$$
where \(V\) is volume in cubic metres and \(A\) is total absorption in metric sabins (surface area times absorption coefficient, summed). The constant 0.161 comes from the speed of sound. Take a bedroom studio of 5.4 m × 4.1 m × 2.6 m, so \(V\) = 57.6 m³, with 9.8 m² of total absorption. Then RT60 = 0.161 × 57.6 ÷ 9.8 = 0.95 seconds. Adding wall panels that lift the absorption to 14.2 m² cuts it to 0.65 seconds.
| Scenario | Volume (m³) | Absorption (m²) | RT60 (s) |
|---|---|---|---|
| Bare studio | 57.6 | 9.8 | 0.95 |
| With wall panels | 57.6 | 14.2 | 0.65 |
T20 and T30 Shortcuts for RT60
A room rarely gets loud enough to measure a full 60 dB fall, so you extrapolate. T20 times a 20 dB drop and multiplies by 3; T30 times a 30 dB drop and multiplies by 2. Both start after the first 5 dB, which skips the early decay time (EDT). Use T20 when your peak is 35 dB above the noise and T30 at 45 dB. Say a 20 dB fall takes 0.41 s: RT20 = 0.41 × 3 = 1.23 s, and a 30 dB fall in 0.62 s gives RT30 = 0.62 × 2 = 1.24 s, a good match.
Averaging Positions and Standing Waves
Standing waves create loud and quiet spots, so measure from several positions and average. Ensemble averaging of the decay curves beats simple arithmetic averaging of the times.
Ideal Reverberation Time for Each Room Type
There is no single best number, because the ideal reverberation time depends on what the space is for. Shorter times favour speech, longer times favour music, and a cathedral can run for seconds by design. A home theater or a recording studio aims lower for tight imaging, while a live room tolerates more. Even a coffee shop suffers when the decay stretches past three seconds, and an acoustically dead room feels clinical.
| Space | Typical reverberation time |
|---|---|
| Classroom | 1 s or less |
| Speech-focused room | about 1 s |
| Conference room or multi-use auditorium | 1.5 to 2.5 s |
| Concert hall | about 2 to 3.5 s |
| Cathedral | 3.75 s or more |
Reverberation Time for Speech Versus Music
Articulation relies on each syllable fading before the next arrives, so comprehension drops as the decay grows. Music, in contrast, gains warmth and fullness from a longer tail.
Reducing RT60 With Absorption and Bass Traps
Acoustic treatment works by adding absorption or removing hard surfaces. Soft furnishings such as curtains and carpet help the mid and high range, and absorptive surfaces like acoustic foam or acoustic panels help further. For the bass, thin products do little: choose a thick bass trap or broadband absorbers, because thickness sets how low the absorption reaches. Diffusion on the ceiling or walls scatters reflections without deadening the room, which keeps its natural life. Treat the floor and glass only after the larger surfaces, and pick durable materials, since the architecture and materials decide how much performance each panel delivers. Whatever you add, measure again to confirm the result.
Why Low Frequencies Make RT60 Uneven
Low frequency waves are long and carry more energy, so bass lingers while high frequencies vanish, leaving a muddy room. Compare octave bands rather than one average, since the wavelength of a 60 Hz note is almost six metres, and check both the high frequencies and bass before you declare the room balanced.
Why a Long Reverb Time Hurts Speech Clarity
With a long reverb time, the tail of one word overlaps the start of the next, so a classroom reading above roughly 1 s on your RT60 result is where intelligibility and clarity begin to suffer. A university classroom study rated speech harder to understand as the decay lengthened, so shortening the figure you measured is the fastest route to clearer speech.
ISO 3382 Standards for Acoustic Quality Reports
ISO 3382 is the international standard for measuring room acoustics, and a compliant report lists RT60 per octave band, source and microphone positions, and the method used. Following the standard keeps your acoustic quality results comparable with anyone else's and makes before-and-after performance claims honest.