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FocusPod Max™Reverberation Time
Definition
Reverberation Time
What RT60 measures, what a good value looks like in an office, and why it matters more than raw volume.
Reverberation time is how long sound takes to fade away in a space once the source stops. The standard measure is RT60 — the time in seconds for sound to decay by 60 decibels. A hard-surfaced room might have an RT60 of 1.5 seconds; a well-treated office sits around 0.4 to 0.6 seconds. Long reverberation makes speech harder to understand, which is why open-plan floors with hard finishes feel exhausting even when they are not especially loud.
How reverberation time is measured
RT60A sound source is generated in the space and then stopped, and the decay is measured. RT60 is the time taken for the level to fall by 60 dB. In practice the measurement is often taken over a smaller decay range and extrapolated, because a full 60 dB drop requires an impractically loud source.
It is frequency dependent. A room can have a short reverberation time at speech frequencies and a long one at low frequencies, which is why a space can sound crisp for conversation and still feel boomy when a door slams.
What good looks like
Typical values0.4 to 0.6 seconds — well-treated open-plan office. Speech is clear, the room does not feel harsh.
0.6 to 0.8 seconds — typical untreated office with carpet and some soft furnishing. Workable but tiring over a full day.
0.8 to 1.2 seconds — hard-surfaced space. Concrete, glass, exposed ceilings. Speech intelligibility drops noticeably and people raise their voices, which compounds the problem.
Above 1.5 seconds — atriums, warehouses, converted industrial space. Fine for the aesthetic, difficult for concentration.
Why it matters more than loudness
The Lombard effectLong reverberation degrades speech intelligibility, so people unconsciously raise their voices to compensate. Everyone else does the same, and the ambient level climbs. This is the Lombard effect, and it is why a hard-surfaced office gets progressively louder through the day without anyone deciding to be loud.
The result is that reverberation, not volume, is often the root cause of a noisy floor. Measuring decibels alone can miss it entirely — the space is loud because it is reverberant, not reverberant because it is loud.
How to reduce it
Absorption, in the right placesReverberation is reduced by absorption, which is what NRC measures. Adding absorptive surfaces — acoustic ceiling treatment, wall panels, carpet, soft furnishing, planting — shortens the decay.
Ceiling treatment usually gives the most return, because in a typical office the ceiling is the largest uninterrupted hard surface and sound reflects off it repeatedly.
What absorption will not do is give anyone privacy. A treated open-plan floor is more comfortable and less tiring, but a conversation at a desk is still audible to everyone nearby. Containing speech requires an enclosure, which is a different problem with a different solution.
Common questions
What is reverberation time?
Reverberation time is how long sound takes to fade in a space after the source stops. The standard measure is RT60, the time in seconds for sound to decay by 60 decibels. Longer reverberation means sound persists and overlaps, which reduces speech intelligibility.
What is a good reverberation time for an office?
Between 0.4 and 0.6 seconds is generally considered good for an open-plan office. Typical untreated offices sit around 0.6 to 0.8. Hard-surfaced spaces with concrete, glass and exposed ceilings often exceed 1.0 second, where speech intelligibility drops noticeably.
What does RT60 mean?
RT60 is the time in seconds for sound pressure in a space to decay by 60 decibels after the source stops. It is the standard expression of reverberation time and is frequency dependent, so a room may have different values at speech frequencies and low frequencies.
How do you reduce reverberation time in an office?
By adding absorption. Acoustic ceiling treatment usually gives the most benefit because the ceiling is typically the largest uninterrupted hard surface. Wall panels, carpet, soft furnishing and planting all help. Absorption reduces reverberation but does not create privacy.
Does reverberation time affect speech privacy?
Indirectly. High reverberation makes speech less intelligible at distance, which slightly reduces how much of a conversation carries. But it also causes people to raise their voices, which more than cancels that out. Absorption is not a privacy solution.
Related: NRC rating · STC rating · sound masking · full glossary
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