Play a sweep through your speakers, record how the room responds with the microphone and get the impulse response: reverberation (RT60) by bands, real bass resonances, a waterfall and EQ suggestions. No REW install, no driver setup.
Measure room acoustics online, straight from the browser and without installing REW. The tool plays an exponential sine sweep through your speakers, records the room with your microphone and computes the impulse response, the same ESS technique behind REW.
From that impulse response it derives the RT60 reverberation time by bands (Schroeder integration), the in-room frequency response, the real bass resonances of your room, a waterfall of how they decay and corrective EQ suggestions ready for Equalizer APO or a miniDSP.
Honest scope and what to trust
RT60 and the mode frequencies are the reliable outputs; the frequency response is relative, not a lab measurement. With an uncalibrated phone or laptop mic the curve's shape is very informative (peaks, dips, tilts), but its absolute values are not, and below about 100 Hz a phone mic is only indicative. What survives beautifully is exactly what you need to treat a room: how long it rings and at which frequencies. Measuring RT60 from the integrated impulse response is what ISO 3382-2 defines, and the exponential sweep the tool uses is the method Angelo Farina formalised. If you own a measurement mic (UMIK-1, iMM-6), load its calibration file and the curve gets corrected, locally, with nothing uploaded.
| Output | Reliability | Why |
|---|---|---|
| RT60 by bands | Reliable | Depends on relative decay, which survives browser latency. |
| Mode frequencies | Reliable | It's the position of the peaks, not their level. |
| Response shape (peaks/dips) | Indicative | Great to compare and spot problems, not calibrated. |
| Absolute level in dB | Not reliable | Uncalibrated mic; below ~100 Hz a phone is only indicative. |
How to measure step by step
A measurement takes under a minute of sweep and hands you the RT60, the response and the waterfall. These are the steps.
- Set up the speakers and the mic. In the browser, turn off any "audio enhancements"; the tool already disables the mic's AGC, echo cancellation and noise suppression.
- Put the mic at your listening position, raise the volume to a clear mid-high level and check the signal-to-noise reading before committing.
- Launch the sweep and stay quiet; a longer sweep (5–10 s) buys immunity to noise.
- Read the RT60 by bands, the in-room response and the waterfall; a ridge that lingers is a mode that rings.
- Apply the suggested EQ to peaks only, or treat the room; type your dimensions to cross-check the measured peaks against the theoretical modes.
When to measure room acoustics for real
Measure once the room is set up and you want the truth instead of a prediction. All you need is a phone or laptop and its microphone, no REW install and no drivers. A measurement mic is the biggest upgrade, though it's optional. Where a calculator predicts an ideal box, this shows what your furnished room does, peaks included. To compare the two, open the room acoustics calculator with your dimensions and line up the theoretical modes against the ones you just measured.
Five situations where measuring the room helps
Measuring pays off at five specific moments: before buying panels, when chasing a boom, after automatic calibration, to check treatment and to place the subwoofer. One by one.
Before buying panels: measure the real RT60
Before spending on absorption, a measurement tells you how much you need. If the RT60 reads 0.6 s and your target is around 0.3–0.4 s, you know how much broadband absorption to add and where. Our guide on measuring your RT60 before buying panels turns that figure into panel count and thickness.
Hunting down the mode that booms
When one bass note is far louder than the rest, the frequency response and the waterfall name the culprit. A peak at, say, 48 Hz that keeps ringing line after line is a length or width mode. Move the seat or the sub, or cut that frequency with one narrow EQ band, then measure again.
Checking automatic calibration (Audyssey, Dirac)
After your AVR's auto-calibration, a measurement shows what it actually did. Room correction sometimes over-flattens the bass or leaves a mode untouched; a sweep at the seat reveals whether the curve is smooth or still has a peak. Set the AVR to stereo/direct so you measure the room, not an upmix.
Seeing whether the treatment worked
Compare before and after: measure, add the panels and measure the RT60 by bands again. Treatment usually tames the mids and highs first and leaves the low bass livelier, which the band-by-band RT60 makes obvious. It's the honest way to know a purchase earned its place.
Finding the best subwoofer position
Try two or three spots for the sub and keep the one with the flattest response at your seat. Each position excites the modes differently, so half a metre changes the bass more than any EQ tweak.
| RT60 | Verdict | What to do |
|---|---|---|
| Under 0.3 s | Dry | Good for critical listening and cinema. |
| 0.3–0.55 s | Adequate | Fine for domestic listening. |
| Over 0.55 s | Live | Add rugs, curtains and broadband absorption. |
Frequently asked questions
How does it measure the room from a browser?
It plays an exponential sine sweep (the same ESS technique used by REW and pro tools), records it with your mic, and deconvolves the capture against the sweep's inverse filter in a background worker. The result is the room's impulse response, from which it derives RT60 (Schroeder integration), the in-room frequency response, modal peaks and a bass waterfall.
What can I trust, exactly?
RT60 and mode FREQUENCIES are robust: they depend on relative decay and peak positions, which survive browser latency and an uncalibrated mic. The frequency response is relative — its shape is informative (peaks, dips, tilts) but absolute levels are not, and a phone mic is only indicative below ~100 Hz.
Can I use a measurement microphone?
Yes, and it's the biggest upgrade: plug a USB mic like the UMIK-1 (or an iMM-6 on a phone), select it as input, and load its calibration file with the “Mic profile” button. The curve is then corrected with the manufacturer's data — the file is read locally and never uploaded.
What do I do with the EQ suggestions?
They are peaking filters (frequency, negative gain, Q) that tame the detected modal peaks. Copy them into Equalizer APO, REW, a miniDSP or your AVR's PEQ. Only cut peaks: nulls are cancellations that EQ cannot fill — those need repositioning or bass traps.
Why do my results change between runs?
Small mic movements change the standing-wave pattern at the mic position — that's room acoustics, not a bug. Keep the mic in the same spot, run a longer sweep for noisy rooms, keep quiet during the measurement, and compare like with like.
Do I need to install an app, or is the browser enough?
The browser is enough for the two reliable outputs, RT60 and mode frequencies: it plays the sweep and records with getUserMedia, no install and no drivers. Native apps and desktop tools exist, but for a quick, honest read of how your room behaves you don't need one.
How is this different from REW?
REW is the desktop standard: more features, mic calibration, an SPL reference and file export, but you install it and set up drivers. This runs in the browser with the same ESS sweep and Schroeder RT60, aimed at a fast diagnosis. Reach for REW when you need deep analysis or documented, calibrated numbers.
Does it work in a large room or a home cinema?
Yes. Use a longer sweep (5–10 s) for more noise immunity, keep the room quiet and measure at the main seat. Bigger rooms have lower, more widely spaced modes, which the RT60 by bands and the waterfall show clearly; just don't expect trustworthy level below ~40 Hz from a phone mic.