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Old 23rd September 2012
  #5
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Aperiodic modulation for acoustic diffusers

Quote:
Originally Posted by John White View Post
Can the dimensions be changed in proportion? In other words, can the one's be two's and the two's four's, etc...so that it can be changed easier to imperial measurements and accessible materials?

Also, other than the "mounting modules" can periodicity be addressed through inverse panels?
Good questions!

If you scale the dimensions the performance will change. While it will still function as a diffuser, I don't know if the performance will be satisfactory. The easiest way to tell would be to test it using AFMG Reflex software. (My demo of the software has expired, but if I install it on another machine any time soon I'll try that simulation. Until then, maybe someone else who has AFMG Reflex would like to try simulating it?).

Aperiodic Modulation
Regarding inverse mounting: I actually optimized the designs in an aperiodic array, modulated using the sequence {1 0 1 1 0}. But during optimization the lowest profile design (called A1-LF) converged to be symmetrical... therefore, whether you reverse the modules or not, it's periodic. In other words, the best solution found by the algorithm (optimization combined with a phyisal model) was a symmetrical diffuser module.

The other stepped diffuser design mentioned in the thesis (called B2-LF) is not symmetrical, and is therefore aperiodic (because it's modulated with the sequence 1 0 1 1 0). While the aperiodic designs offer better performance, they are more complex in shape and deeper in profile.

Because the aperiodic designs are less elegant, they are less suitable as DIY diffusers. I did not create detailed blueprints for them, but if you wish to build them, the specs are in Chapters 7.3 and Chapter 8 of the thesis.


Optimizing for both Depth and Performance
I should clarify that I was optimizing for depth, not simply performance.

The low profile, symmetrical design (A1-LF) was optimized to have good performance, while being super low profile.

The asymmetrical design (B2-LF) achieved better performance, but with a deeper depth.


Hope I'm not being too confusing. Does that make sense to you?

-Tim