RT60 is one of the key indicators used to describe room acoustics. It represents the reverberation time: the time required for sound to decay by 60 dB after the source has stopped. Measuring RT60 helps determine whether a room is too echoey, too dry or well balanced.
Why RT60 matters
Long RT60 values create a constant echo effect: blurred speech, loud background noise, listening fatigue. Very short RT60 can make a space feel unnaturally “dead”. Depending on the use, target values differ:
- Around 0.6 s for classrooms and meeting rooms.
- 0.55–0.77 s for offices, corridors, lobbies and calm restaurants.
- Shorter for studios, different for performance spaces.
What you need for a simple measurement
- A smartphone with a decent microphone.
- An acoustic measurement app (if available) that can analyse RT60.
- Or a basic “clap and record” approach for a first estimate.
For critical projects, a professional acoustic measurement is still recommended.
Step-by-step measurement method
1. Prepare the room
- Close doors and windows.
- Keep furniture in its usual position.
- Minimise background noise (HVAC, machines, traffic).
2. Generate an impulsive sound
The idea is to create a short, sharp sound and analyse how it decays:
- A strong hand clap.
- A balloon pop.
- A short, dry impact (board hit, etc.).
3. Record the decay
Place the smartphone around the listening area, start recording, produce the impulsive sound, let the reverberation die away, then stop recording.
4. Estimate RT60
Some apps can calculate RT60 directly from the signal. Otherwise, simplified methods can provide an approximate value based on the decay curve. The goal is to obtain a realistic order of magnitude rather than lab-grade precision.
Interpreting the result
- RT60 much higher than your target: the room is too reverberant.
- RT60 much lower: the room may feel overly dry.
- RT60 close to recommended values: acoustic comfort is generally acceptable.
Visual inspection of the space (hard surfaces, high ceilings, parallel walls) helps refine the diagnosis.
From measurement to treatment
Once RT60 is known, you can size the required absorbing surface on ceilings, walls or furniture. The Tester / Acoustic tool helps estimate how much absorption is needed to reach the target RT60.
Impact on user experience
Controlled RT60 improves speech clarity, reduces background noise and contributes to overall comfort. See acoustic project examples on Inspiration.
Conclusion
Even with simple means, measuring RT60 provides valuable insight into room behaviour and supports informed decisions about acoustic treatment.