Archive site for Autodesk Ecotect Analysis educational resources, notes and tutorials



Ecotect Tutorial : Optimum Reverberation Times

Synopsis

Speech and music have very different acoustic requirements. This tutorial looks at how to interpret these requirements in relation to a statistical RT graph in Ecotect.

Duration

You will need about 40 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 SimpleTheatre.eco example file. This can be found in the 'Examples' folder of your Ecotect installation.

Tutorial

  1. Open the SimpleTheatre.eco file in Ecotect, and generate a statistical RT graph via the Calculate menu.
  2. In the settings and options below the graph, make sure the Auditorium Seating is set to a value greater than zero, say 250. Click the Calculate button, and blue bands will appear across the RT graph, indicating the optimum RT range for speech and music.
  3. The frequency of speech falls within a relatively narrow band, between 500Hz and 4kHz. The optimum RT is around 1.1 seconds for mid-frequencies, so as to minimize blurring of words. This is represented by the lower half of the blue band.
  4. Music covers a much wider range of frequencies, anywhere between 20Hz to 20kHz, and generally benefits from longer reverberation times. This is represented by the upper half of the blue band. However, note that different styles and genres of music may have different RT requirements.
  5. The RT of a space is affected by a number of different factors. For example, varying the capacity of the auditorium seating, the occupancy rate and the type of seating will change the RT. Try changing these options and then click the Calculate button to see their effect on the RT graph.
  6. The materials of the room surfaces will also affect the RT, due to the different absorption coefficients of building materials. Try assigning different materials to the walls and floors of the models to see their effect on the RT graph.
  7. Note also that the various RT algorithms predict different statistical results for the space, based on the various auditorium settings and material assignments you select. To determine which algorithm is most appropriate for your analysis, set the Reverb Time Algorithm drop list to Automatic.
  8. Whether or not a space has good acoustic performance is subject to a variety of factors, and is very much influenced by the way in which the space is intended to be used. Ideally, the most appropriate algorithm line should fall within the blue bands for either speech or music, depending on intended use. You should also pay attention to how the RT varies based on frequency, as the frequency bands for speech and music vary considerably.
  9. In summary, there can never be a space which is totally ideal for both speech and music, unless it is adjustable either in volume or in the nature of its surfaces so as to change its reverberation time. One use usually has to take precedence over the other. Unless electronic amplification is to be in constant use, this tends to be the speech application.
Ecotect Tutorial : Linked Acoustic Rays
Ecotect Tutorial: Statistical Reverb Time Graphs

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