Reverberation Time (RT) is defined as the time it takes for sound to decay by 60 decibels (dB).
The Reverberation Time of a room is crucial to determine when working to improve acoustics. An RT that is not appropriate for a room's intended application can lead to a lack of clarity and intelligibility.
The ideal RT for a space depends on the room's physical volume and its intended application. For example, spaces primarily used for speech generally require a shorter RT than those used for music. Some spaces involve both speech and music; finding a target RT that works well for both is important.
RT is frequency dependent. The size and shape of the room, as well as the surface materials within it (such as carpet vs. tile, concrete vs. drywall, padded chairs vs. wooden pews), significantly impact the RT across the frequency spectrum. For instance, a room might have a long RT in the low frequencies (e.g., 2-4 seconds) and a shorter RT in the mid/high frequencies (e.g., 1-2 seconds). This imbalance can make a room sound "boomy" or "muddy", hindering effective communication.
Understanding and managing reverberation time is essential for good room acoustics. Proper selection and placement of absorptive, reflective, and diffusive surfaces help achieve an acceptable RT. Absorption materials, like our FulFill Panels, reduce RT by absorbing sound energy. Thicker absorption panels are generally more effective at absorbing lower frequencies. (compare 2" FulFill to 4" FulFill at 125Hz, for example) Diffusion treatments (custom Diffusers, Diffuser 4-Packs, and our Flex-48) scatter sound, reducing harsh reflections while maintaining some liveliness.
The concept and definition of reverberation time originated from the work of Wallace Sabine, a professor at Harvard University who is considered the grandfather of architectural acoustics. Sabine was tasked with improving the acoustics of a poor-sounding lecture hall and became curious about why it differed from the great acoustics at Sanders Theater.
Through experimentation, including using seat cushions from the Sanders Theater in the lecture hall and measuring the decay of sound with an organ and a stopwatch, Sabine developed the first equation for reverberation time, known as the Sabine equation. We use this formula daily in our RT Models when developing our custom Treatment Plans.
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