RT60 (reverb time)

In a reverberant room, sound continues to reflect after the source stops. RT60 describes the decay from the sound level before that stop to a level 60 decibels lower. A full 60-decibel decay may be difficult to measure in a noisy room, so practitioners often estimate it from a shorter section of the measured decay curve. The calculation and reported method should be clear when results are compared.

A room does not have one universal RT60 value across all frequencies. Furnishings, surface materials, room volume and boundary construction affect each frequency band differently. A value averaged across a broad range can hide a bass decay problem or a short high-frequency decay. Measurement positions matter too, because sound fields are not perfectly uniform, especially in small rooms.

RT60 is commonly measured by exciting a room with a test signal and recording how sound decays, or by analyzing a suitable impulse response. Background noise, source directivity, microphone response and the room's shape influence the measurement. A clap or phone application may help reveal a rough issue but should not be treated as a calibrated assessment.

Decay affects how quickly one sound becomes distinct from the next. A long reverberation time can blur speech or musical detail in a small production room, while a more lively decay may be desirable for performance. Control rooms generally need a response that supports reliable listening, but the appropriate target depends on size, use and monitoring arrangement.

RT60 helps describe and compare room behavior and can guide decisions about acoustic treatment. It does not alone describe frequency response, echo timing, stereo image or transmission to other spaces. Two rooms with the same reported decay time may sound different because their reflections, dimensions and frequency balance differ.

A useful assessment records decay in frequency bands and uses repeatable source and microphone positions. The room should be in its normal operating state, including furnishings and doors, and the test should provide enough signal above the background noise. If conditions change, such as adding people or equipment, the measured decay may change as well.

Do not interpret a single RT60 number as a treatment prescription. A long decay at one frequency may call for a different intervention from an early reflection or a strong modal peak. Porous panels and bass traps affect different ranges according to their design. A diffuser changes reflection direction rather than simply shortening decay. Combine measurements with listening and an understanding of the room's purpose.

A Dubai media room is used for editing spoken interviews and reviewing music. Editors describe dialogue as tiring, but the room's furnished and unfurnished states differ. A consultant measures decay in frequency bands using a consistent speaker and microphone setup, first with the room in normal use and then with the empty floor area exposed.

1. Record the measurement positions, source level, microphone and room furnishings.
2. Check that the decay is sufficiently above background noise for a meaningful estimate.
3. Review frequency-band results instead of relying on a single average value.
4. Identify whether the dominant concern is overall decay, a narrow low-frequency tail or an early reflection.
5. Make a targeted change and repeat the measurements under the same conditions, then listen to speech and music.

The results show that frequency behavior is uneven, so the team chooses treatment for the observed range rather than making the room uniformly more absorptive. The notes preserve the original setup and method, allowing later measurements to be compared fairly. When the room is rearranged months later, the team repeats the same positions before judging whether the change improved or degraded the decay.

• Treating RT60 as one fixed number ignores frequency and position differences.
• Comparing results from different methods or room states can suggest a change that is not real.
• Using a clap as a precise measurement overlooks source, microphone and noise limitations.
• Trying to minimize decay without considering the room's musical or recording purpose can make it unpleasantly dry.
• Assuming RT60 describes soundproofing confuses internal decay with transmission between spaces.

Report the method, frequency bands and room state alongside results. Use RT60 as one useful description of room decay, not as a complete score of acoustic quality or a guarantee of how a recording will sound.