RevMeter Pro 4‏+

RevMeter Pro measures the reverberation time of a room.
Burst and interrupted modes are supported. Because the dynamic range of the
iPhone microphone (30dB - 100dB) is too low to get 60dB dynamic RevMeter Pro supports only the RT30 and RT20 method.
RevMeter Pro also lets you send the measured results by eMail for later analysis. In addition screenshots
may be saved to the iPhoto album.

Definition of Reverberation Time:
The Reverberation Time RT60 is defined as the time required for reflections of a
direct sound to decay by 60 dB below the level of the direct sound. As it is usually very
difficult to achieve a dynamic range of 60dB two more methods have been established. They
are called RT30 and RT20. The measured time is the multiplied by 2, respectively 3 to
compute the RT60 time.

Measuring the reverberation time:
Historically reverberation time could only be measured using a level recorder
(a plotting device which graphs the noise level against time on a ribbon of moving paper).
A loud noise is produced, and as the sound dies away the trace on the level recorder will show a
distinct slope. Analysis of this slope reveals the measured reverberation time. Modern digital
sound level meters can carry out this analysis automatically.
Two basic methods exist for creating a sufficiently loud noise (which must have a defined cut off point).
Impulsive noise sources such as a blank pistol shot, or balloon burst may be used to measure the
impulse response of a room. Alternatively, a random noise signal such as pink noise or
white noise may be generated through a loudspeaker, and then turned off.
This is known as the interrupted method, and the measured result is known as the interrupted response.

Disclaimer:
Even though the RevMeter Pro Software has been calibrated using professional grade equipment, do no use RevMeter Pro
to carry out professional measurements. The author can not be held liable for any damage which might arise by using RevMeter Pro.