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Ecotect Tutorial: Statistical Reverb Time Graphs

Synopsis

This Ecotect tutorial demonstrates step by step how to display and interpret information contained on a Statistical Reverberation Time graph.

Duration

You will need about 20 minutes to complete this tutorial.

Training and Accreditation

Successfully completing this tutorial fulfills one of the practical skills required for completing Level 1 of the Acoustic Design training module.

Resources Required

To complete this tutorial, you will need the AcousticRays.eco example file. This is contained in the 'Examples' folder located in the folder where Ecotect is installed on your computer.

Tutorial

  1. In Ecotect, open the AcousticRays.eco file located in the Examples folder. The file contains a model of an example auditorium.
    The AcousticRays.eco example file.
  2. Go to the Calculate menu, and select the Statistical Reverberation... menu item. This will display a graph for calculating statistical reverberation times.
    Find Statistical Reverberation... in the Calculate menu.
  3. Alternatively, you can click on the Analysis tab on the left had side of the Ecotect workspace, and then click the Reverberation Times tab located in the bottom half of the workspace.
    The Statistical Reverberation Time control panel.
  4. Select the zone for which you want to display statistical reverberation times - you can do this using the pull-down menu under the Selected Zone section located near the bottom left hand corner of the screen. In this example model, there is only one zone called Main Hall.
  5. Under the selected zone, Ecotect displays the volume for the selected zone. This is calculated based on volume of the zone as modeled in the 3D Editor. If you wish to quickly see the effect on reverberation time by changing the volume of the space (without having to edit your Ecotect model), you can manually type in the volume. To reset the volume to the zone volume as modeled, just click the Recalc button.
  6. If not already visible, now click the Calculate button to display the Statistical Reverberation Time graph. You will see a graph similar to that shown below :

    A statistical reverberation time graph.
    The horizontal axis of the graph displays the audible frequency ranges of sound, while the vertical axis displays the reverberation time in milliseconds. The blue banded section of the graph is the ideal zone in which the reverberation time for the zone should occur - note how music has a slightly longer ideal reverberation time compared to speech.
  7. The blue, green and red graphed lines represent the calculated reverberation times for the selected zone, each representing a different reverberation algorithm as shown in the legend. To selectively highlight the different algorithms, select the required one from the Reverb Time Algorithm pull down menu. If you select Automatic, Ecotect selects the most appropriate based on overall absorption levels.
  8. The capacity and type of seating for your zone can have a significant impact on the calculated reverberation times. Under the Auditorium Seating section, you can adjust the number of seats, the type of seating, and the occupancy level. Once you have finished your adjustments, click the Calculate button again to see what impact these changes have on the calculated reverberation time.
    Auditorium Seating.
  9. Under the Select Display Type pull down menu in the Calculation section, you can choose how the algorithms are displayed. All Algorithms is the default display option, which shows all the different algorithms simultaneously. Selected Algorithm shows the selection as specified under the Reverb Time Algorithm pull down menu. Occupancy Range shows the reverberation times (for the selected algorithm) for when the zone is empty, full, or occupied as the specified capacity.
  10. Lastly, the right hand side of the reverberation time control panel contains a text field which displays a summary of the selected zone and settings, along with a table of reverberation times for different frequencies. All of this information can be copied (Ctrl-C) and pasted in a seperate document (Ctrl-V) for report writing purposes.

Further Reading

  • In order to be able to calculate reverberation times, the selected zone must be a fully-enclosed thermal zone. Refer to the Zone Management tutorial for more information about thermal zones.
  • The assigned materials for different surfaces in your zone/model will have an effect on calculated reverberation times.
  • For more information about the different algorithms Ecotect uses to calculate reverberation times, please refer to the following wiki pages :
    • Sabine Algorithm
    • Millington-Sette Algorithm
    • Norris-Eyring Algorithm
  • You can also calculate reverberation times using random and acoustic analysis. Please see the Calculating
  • For a description of the icons docked to the side of the Reverberation time graph, refer to the Working with Graphs Ecotect tutorial.
Ecotect Tutorial : Optimum Reverberation Times
Ecotect Tutorials : Reverberation Time Algorithms

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