Larson Davis System 824, Руководство по обучению

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3/22/01 RT60 Measurements 3-1
C H A P T E R
3
RT60 Measurements
The versatility of the 824 includes the measurement of RT60
or reverberation time. This capability combined with
advanced triggering features allows the use of a noise gener-
ator without an interconnecting cable to the 824.
Those of you involved in determining decay times of rooms,
theatres, or any acoustic space designed for a specific acous-
tic application or in analyzing the absorptive qualities of
walls, doors, barriers or partitions will find the 824 to be a
valuable tool in your arsenal.
What is an RT60 and how is it measured?
RT60 Defined
Sound decay measurements are used to determine the sound
absorption characteristics of a room. This is also known as
the reverberation time or the decay time.
The reverberation time in a room at a given frequency is the
time required for the sound pressure level to decay from a
steady state value by 60 dB after the sound suddenly ceases.
For example: A room is excited with a gun blast or a balloon
pop and the maximum sound pressure level reached is 115
dB. RT60 is the amount of time it would take for the room to
absorb the acoustic energy such that the sound pressure level
reaches 55 dB. Typical values of reverberation times are
between .01 to 3.5 seconds.
Though RT60 specifies that the time be measured for a level
drop of 60 dB it is unlikely that 60 dB drop be obtained.
Therefore, RT60 is actually a slope function with the drop of