What is Reverberation Time (RT60)?

• A. RT60 is the time it takes for sound to decay by 60 dB.
• B. RT60 is the time it takes for sound to decay by 6 dB.
• C. RT60 is the time for sound to start in a space.
• D. RT60 is the level of background noise in decibels.

Answer: (A)

RT60 is the time it takes for the reverberant sound level in a space to decay by 60 decibels after the sound source stops. This standard reference point captures how long reflections continue to be audible and is influenced by room size and surface absorption. The other options describe different ideas—6 dB decay isn’t the standard RT measurement, the time for sound to start is about onset rather than decay, and background noise level is about ambient sound, not decay time. In practice, you measure RT60 by producing a loud broadband impulse, recording the decay, and finding how long it takes for the SPL to fall 60 dB in a given frequency band.