Measuring Reverberation Time

We will use the software package Audacity to record and analyze sound tracks.  Audacity is free, open-source software that runs on Mac OS X, Microsoft Windows, GNU/Linux, and other operating systems.  It can be downloaded from http://audacity.sourceforge.net/ .

1. Do trial run of claps to set recording level.
2. Record 4 claps.  Time between claps should be long enough for sound to die completely.  Include a second or two of silence either at the end or beginning.
3. Remove noise.

1. Select region of silence.
2. Under Effects menu, select Noise Removal.  Click on Get Noise Profile.
3. Select All of the recorded track. (Ctrl-A)
4. Go back to the Noise Removal and click on Remove Noise.
5. Listen to edited track to hear effect of noise removal.  Was too much noise removed?

4. Under Audio Track menu, select Waveform (dB) option.
5. Select best looking clap.
6. Select Fit in Window.  (Ctrl-F)
7. Find ∆dB/∆t.  Highlight a linear portion of the decaying waveform. 
8. Using the ratio ∆dB/∆t = 60db/T_reverb , solve for T_reverb.  ∆dB can be found from the vertical scale.  ∆t can be found from either the time scale at the top of the waveform or from the reading in the status bar at the bottom of the window.
9. Calculate or estimate the volume of the room.
10. Using the volume of the room and the measured T_reverb determine the type of events for which the room is appropriate.

Above graph is from our textbook "The Science of Sound" 3rd. edition by Rossing, Moore, and Wheeler, Addison Wesley Publishers, 2002.