3M DL, SE Reverberation time RT60, Reverberation RT60 methods, DB level Decay Curve, DB level2

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Reverberation time (RT60)

Reverberation time (RT60)

Reverberation time is a measurement used to evaluate and measure sound decay in a specific space, tailored to speech or music, such as: classrooms, auditoriums, gymnasiums, concert halls/theatres, (etc..). For room acoustic, results are used to ensure quality sound is evenly dispersed throughout a specific room with limited echoes/refractions. For music or performance auditoriums (i.e., symphonies), higher reverb. time is preferred so the ending results are more robust.

The Reverberation Time over each octave band can be analyzed using a decay curve. Each octave band shows the time of sound at the start and after the activation of the noise system using either interrupted or impulse sound methods.

The example below displays the Reverberation Time in an enclosed room. How it is measured with the impulse method: (1) A starter gun provides a broad impulsive spectrum noise at 110 dB. The instrument automatically begins plotting the sound decay (see dB level 1) and stops as the noise falls off (see dB level 2). Hence, the rate of decay is calculated from decay curve (or regression line) which will give you the rate of decay in the room. The RT60 measurement is calculated with the Txx time (i.e., T20) factored in and extrapolated to a 60 dB drop.

dB level 1

Decay Curve

Drop of sound pressure from Maximum to its ambient background level.

dB level2

Figure 6-1: Reverb Time

Reverberation (RT60) methods

The two methods supported by the SoundPro are the Interrupted noise method and the Impulse noise method. While the initial sound source used is different, the ending decay curve results are very similar providing accurate RT60 measurements.

Models SE and DL