Go looking for an app to measure RT60 and you mostly turn up SPL meters. Plenty of them call themselves “acoustic measurement” tools, yet few can actually produce an RT60 figure. So let’s sort the main acoustic measurement apps by one thing: can they measure RT60 at all.
Conclusion
The right pick depends on what you’re doing.
- To stay on a single phone, go with Sonir. It’s one of the few mobile apps that captures an impulse response from a sweep and derives RT60 automatically.
- If a computer is on hand, REW is the fastest route, and it’s free. It’s the de-facto standard for RT60. The catch: desktop only, nothing you carry around.
- For serious UMIK calibration, SignalScope. Solid measurement bones, but an expert-facing UI.
- If you only want SPL and a live spectrum, Decibel X. The modern UI is a draw — but RT60 is outside what it does.
Comparison table
The first big split is simply whether the app can output RT60.
| App | RT60 (sweep → IR) | Calibration file | Recording comparison | Platform | Pricing |
|---|---|---|---|---|---|
| Sonir | Yes, automatic | Yes (.txt) | A/B + ABX | iPhone / iPad / Android | Free + Pro |
| AudioTools | Yes, dedicated module | Yes | Partial (seat-to-seat) | iOS / Mac | One-time + tiered IAP |
| SignalScope X | Yes, higher tiers | Yes (UMIK) | No | iOS / Mac | Subscription |
| Decibel X | No, SPL/RTA focused | Limited | No | iOS / Android | Free + sub/buyout |
| REW | Yes, the standard | Yes | No | Windows / Mac / Linux | Free |
For comparing the recordings themselves (air-recording comparison), there are also WuTools (web) and Youlean (LUFS/DR) outside this table, but those aren’t RT60 tools, so they sit on a different axis. Covering recording comparison and RT60 measurement in one app currently leans toward Sonir.
What it means to actually “measure” RT60
This is the crux of choosing an app, so I’ll spend a bit longer here. An SPL meter only reads how loud the sound is right now; an RTA only shows the spectrum of what’s playing right now. Neither tells you how the room is coloring that sound. RT60 goes after the room’s response itself, which takes a different mechanism.
What you need is the room’s impulse response (IR). Play a rising chirp (a sweep) through a speaker, record it, correct the playback-to-record latency, then convolve with an inverse filter — out comes one IR. RT60 is that IR run through Schroeder integration, with the time for the sound to decay by 60 dB read off the slope. EDT, C50, and the waterfall all derive from the same IR.
So even an app that calls itself “acoustic measurement” can’t produce RT60 if it has no step for capturing an IR. The reason so many stop at SPL and RTA is that this part is a pain to implement. If RT60 is your goal, the fastest filter is to ask first: does it do sweep → IR?
As an aside: most complaints about RT60 coming out absurdly long trace back to clipping in the recording, not the room. However good the app is, if the recording peak is pinned at 0 dBFS, the decay curve flattens. Aim for -6 to -12 dBFS. That holds no matter which app you use.
App-by-app
Sonir
Does sweep → IR → RT60 end to end on mobile. Beyond RT60, a single sweep yields EDT, C50, frequency response, and the waterfall. It watches the recording peak and warns on clipping, so you catch a broken measurement before it happens. A calibration file (.txt) corrects the built-in mic. What nothing else here does: it also overlays recordings in A/B and runs ABX blind tests in the same app. Basic measurement is free; per-octave-band deep dives are Pro. The weak spot is that it’s still a new app with a thin track record.
AudioTools
The veteran of iOS measurement apps, with a dedicated RT60 module and calibration support. Breadth and reliability are high, and it has seat-to-seat comparison. The snags are the dated UI and the pricing — a $19.99 base plus tiered IAP that adds up if you want everything. For serious measurement folk, still a strong choice.
SignalScope X
Strong on UMIK calibration, with arguably the soundest measurement bones of the bunch; higher tiers handle impulse response and reverberation time. It suits people who calibrate carefully and want absolute accuracy. It’s a subscription, and the UI and workflow assume an expert. A little high a bar for anyone who just wants to measure a room casually.
Decibel X
The most modern UI here, and reading SPL and spectrum on it is genuinely pleasant. But at heart it’s an SPL meter, not built to capture a room IR and derive RT60. Install it expecting RT60 and you’ll come away disappointed. It’s also well known for the subscription-backlash reviews. For a quick read on current level and tonal balance, it’s excellent.
REW (the desktop benchmark)
Hard to believe it’s free for what it does. For RT60, waterfall, frequency response — desktop measurement starts with REW and you won’t go wrong. Calibration, external mics, bring anything. Its one and biggest limit is that it isn’t mobile. If you can stomach hauling a laptop, mic, and cables to the room you want to measure, it’s the most capable on features.
Recommendations by use case
- Just want a quick RT60 on your phone: Sonir. Record one sweep and RT60 comes out automatically.
- Building a fixed, serious measurement rig: REW + a calibration mic. Free, most features.
- You want absolute-accuracy calibrated measurement: SignalScope (UMIK) or AudioTools.
- You want to line up recordings and compare them: Sonir (A/B + ABX). Covered in the same app as RT60.
- SPL and the current sound are all you need: Decibel X. Don’t expect RT60.
In short, “measures RT60, is portable, and also handles recording comparison in one app” is Sonir’s position, the inverse of REW. If you can sit at a desk, REW; if you measure in the field, Sonir — that split is close to reality.
FAQ
Is there a free app that measures RT60?
If you can use a computer, REW measures RT60 for free. If you want to stay on your phone, Sonir computes RT60 with its free basic measurement. Decibel X’s free tier centers on SPL and spectrum, so RT60 is out of scope.
Can Decibel X measure RT60?
Not really. Decibel X is built around an SPL meter and a real-time spectrum view, not around capturing the room’s impulse response to derive RT60. If RT60 is the goal, pick a different app.
Do I need a calibration mic for comparisons?
For RT60 or relative comparison on the same device, the built-in mic is fine. You only need calibration when you want absolute-accurate frequency response. SignalScope and AudioTools are strong on UMIK-style calibration; Sonir loads a calibration file (.txt) to correct the built-in mic.
Which is more accurate, a phone or REW?
REW wins on breadth and polish on the desktop. On the phone side, load a calibration file and keep conditions consistent and you reach practical accuracy, with the mobility to carry it to wherever you want to measure. For relative RT60 comparison, a phone is often enough.
Related articles
- How to measure RT60 with a smartphone: RT60 alone, from definition to computation and how clipping breaks the value
- Measuring room acoustics with a smartphone: the full picture of RT60, frequency response, and waterfall
Measure it in Sonir
Sonir is an app that completes acoustic measurement and comparison on your smartphone. The RT60 measurement in this article too — just play the sweep and record, and it derives it from the IR automatically. Line up your recordings under the same conditions and compare them in A/B or ABX. Basic measurement is free; per-band deep dives are Pro.
iOS / Android, coming soon. See the features page.