The reverberation time is an acoustic parameter for the reverberation of a room. To measure the drop in sound pressure level is measured after a short loud noise (pop a bag or clap your hands once). The time it takes for the sound to decay by 60 dB, is called the reverberation time.
When assignment "= 80 dB loud" and "20 dB = quiet" you can also say this: The reverberation time is the time that elapses until you no longer observe a previously loud noise.
In a classroom at school or a in a nursery school, the reverberation time should be about 0.6 seconds. The desirable value is slightly dependent on the volume of the room: 180 m³ = 0.55 s / 360 m³ = 0.65 s.
The value of 0.6 seconds is considered for a full room with students or children. Due to the absorption of the bodies, the reverberation time of an empty room is higher. For an empty room the reverberation time should be 0.75 seconds, instead of the 0.6 seconds for a full room.
For hearing-impaired children or adults with tinnitus the nominal reverberation time can be reduced by 20%.
For comparison: In a room, which is used for music, the reverberation time should be 1.1 seconds, in churches, the value is 2 seconds or higher.
The reverberation time is too long:
In a live room every word sounds louder. Furthermore, a previously spoken word is still audible when the following words are spoken. They talk across each other. To improve the speech intelligibility the speaker speaks louder. Thus, it becomes even louder in the room.
The reverberation time is too short:
Children, standing directly in front of the speaker, understand the spoken words well. Due to high sound absorption in the room, on the side and particularly in the rear area of the speaker, the words are bad to hear. The children do not feel addressed. This can be compensated by speaking louder, but this leads to hoarseness of the speaker.
Measurement of the reverberation time:
Before and during the measurement, it must be quiet in the room. The measurement is triggered by a loud clap or popping of a paper bag. The determined value of the reverberation time is displayed immediately. After a successful statistical evaluation, a green circle appears. For evaluating the average of 3-5 measurements should be used.
(If you need a more fully featured RTA, with 1/1, 1/3 and 1/6 octave display, RT60, Noise Criteria, A&C Weighting etc. combined with a signal generator, please take a look at my "AudioTool" app in Android Market.)
Reverb Time Calculator allows you to estimate the reverberation time of a room making your design from a database with over 200 materials (PRO version) arranged in 18 categories and regularly updated.
The estimation can be performed using the following methods of calculation:
- Eyring (PRO version)
The results given in each design allow to visualize an estimate reverberation time expressed in octave bands (125, 250, 500, 1000, 2000 y 4000 Hz).
These results can be compared with the RT60 values recommended depending on the use to which will be allocated the room (recording studio, broadcast studio, conference room, ...) and its volume, and lets change the materials used to fit desired reverberation times.
The materials available for the design of the room are contained in a database with over 200 materials (PRO version) classified in 18 categories:
Concrete, Bricks, Cellulose , Corks , Crystals, Foams , Cotton Fiber , Fiberglass , Rockwool , Wood, Metal, Furniture , People , Plastics , Rocks , Fabrics , Miscellaneous and Gypsum.
To select each item , you can view the absorption coefficients of each material graphically.
In Lite version the database contains 38 materials (2 materials per category).
Optimized for use in both Smartphone and Tablets.
Currently the application is available in English and Spanish.
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