RT60 calculator Sabine calculation reverb time reverberation time Sabin formula

• Calculation of the reverberation time after Sabine - RT 60 decay •

In 1898, Wallace C. Sabine (Sabin) (1868 - 1919) came up with the reverb time formula, but
the article "Collected Papers on Acoustics" appeared in print 1922:

RT₆₀ = k · V / A

with k = (24 · ln 10) / c₂₀ = 0.049 (feet) and with k = (24 · ln 10) / c₂₀ = 0.161(metric)

V = room volume in m³    A = α · S = equivalent absorption surface or area in m²
RT₆₀ = reverberation time in s    S = absorbing surface in m²
A = α₁ · S₁ + α₂ · S₂ + α₃ · S₃ + .. .          c₂₀ = 343 m/s at 20°C

Sound engineers and "ear people" mostly use the usual sound field quantity, they therefore state:
RT60 is the reverberation time, when the sound pressure level is decreased to (−) 60 dB,
this is the thousandth part (10⁻³) of the initial sound pressure.

Acousticians and "people fighting sound" like more the sound energy quantity. They express
this differently:
RT60 is the reverberation time, when the sound intensity level is decreased to (−) 60 dB,
this is the millionth part (10⁻⁶) of the initial sound intensity.

Reverberation time (RT) is a measure of the amount of reverberation in a space and equal
to the time required for the level of a steady sound to decay by 60 dB after the sound has
stopped. The decay rate depends on the amount of sound absorption in a room, the room
geometry, and the frequency of the sound. RT is expressed in seconds.

k is a constant that equals 0.161 when the units of measurement are expressed in meters and
0.049 when units are expressed in feet.
A = S × α is the total surface absorption A of a room expressed in sabins. It is the sum of all the
surface areas in the room multiplied by their respective absorption coefficients. The absorption
coefficients α express the absorption factor of materials at given frequencies.
V is the volume of the enclosure. The figures used in this calculator come from the table of
absorption coefficients for various materials which can be found in any book that talks about
room acoustics.

Enter the measurements of the room. Make sure you specify the units.

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You will see the program but the function will not work.

Walls	Material	Windows, doors and other surfaces
Walls	Material	Deflection Material	Size	How many
Front			x
Back			x
Left			x
Right			x
Ceiling			x
Floor			x

125 Hz 250 Hz 500 Hz 1000 Hz 2000 Hz 4000 Hz

Estimated RT 60 of this room is seconds.

Absorption Coefficients α of Building Materials and Finishes

The reverberation time is the time interval within which the sound level in a room has faded away
by 60 dB.
Note: This sound pressure is the thousandth part of the initial sound pressure and the sound intensity
is the millionth part of the initial sound intensity. Often this is confusing, because the sound pressure
as a sound field quantity is mixed with the sound intensity as a sound energy quantity. I ≈ p².

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