What Is RT60 and Why Does It Matter for Your Listening Room?

RT60 is the time it takes for a sound in a room to decay by 60 decibels after the source stops. It is the foundational measurement in room acoustics and the number that most directly predicts how clear, detailed, and fatigue-free your system will sound.

When a speaker produces sound in a room, that sound bounces off walls, ceiling, floor, and furnishings. Each reflection takes time to decay. If the decay is too long, reflections stack on top of each other and blur the direct sound from your speakers. Detail collapses. Imaging falls apart. The system sounds diffuse and indistinct regardless of how resolving the speakers are.

For critical listening environments, the widely accepted target range for mid and high frequencies is between 0.2 and 0.4 seconds. This is derived from ITU-R BS.1116, the international standard for critical listening facilities. Rooms in the 0.3 to 0.4 second range tend to feel alive and natural. Rooms below 0.2 seconds can feel unnervingly dead, which fatigues listeners differently. Rooms above 0.5 seconds in a listening context make it difficult to resolve fine detail.

RT60 is not a single number. It is measured across frequency bands, typically at octave or one-third octave intervals from 63 Hz to 8 kHz. Low-frequency RT60 is almost always longer than mid and high frequency RT60 because low-frequency sound requires far more absorptive mass to attenuate. A room with excellent mid and high-frequency decay can still have a bass RT60 of 0.8 seconds or longer, which creates a thick, boomy foundation that muddies everything above it.

The measurement itself is straightforward. A calibrated impulse — either a starter pistol blank, a balloon pop, or a swept sine wave from a measurement system like REW — is captured by a measurement microphone at the listening position. The resulting impulse response shows how quickly energy at each frequency band decays. Most acoustic analysis software calculates RT60 automatically from this data.

Reducing RT60 requires adding absorption to the room. Acoustic panels using rockwool or rigid fibreglass are the standard treatment. Thick panels placed at first reflection points on side walls and the ceiling between the speakers and listening position address mid and high frequency energy first. Broad-spectrum absorption from floor-to-ceiling panels or panels angled in corners addresses a wider range.

Bass RT60 reduction requires different treatment. Low-frequency energy penetrates standard acoustic panels and reflects off the structural elements behind them. Corner bass traps are the most effective treatment — floor-to-ceiling mineral wool in all four vertical corners addresses the frequencies where room modes concentrate energy. Superchunk bass traps, which fill the entire corner cavity with absorptive material, are the most effective approach available to most residential spaces.

Diffusion also plays a role. Scattering devices distribute reflections across time and direction rather than eliminating them. The result is a sense of spaciousness and envelopment without lengthening the perceived RT60. A well-designed room blends absorption and diffusion rather than treating acoustics as purely a problem of removing reflections.

A professional acoustic assessment measures RT60 across all relevant frequency bands at multiple microphone positions, compares the results to target ranges for the room's intended use, and produces a prioritized treatment plan. This removes the guesswork from acoustic treatment and ensures your investment in panels and bass traps addresses the actual problem rather than the assumed one.