Acoustic Scattering Research – The Setup

Acoustic scattering is a measure of how well a surface can spread sound energy evenly in all directions.  The concept is simple enough, but achieving the evenness part can be difficult to design for given the complexity of how spaces are shaped, material properties, and how sound behaves.  This is why we have acoustic consultants on projects, particularly when performance spaces are involved, because the consultants bring knowledge and familiarity that we as architects likely don’t possess.  Sometimes this collaboration leads to new questions or proposals that neither party has enough information to properly judge.  What better way to get that information then to do some research.

Digital Model of the Goniometer (courtesy David T. Bradley)
Digital Model of a 3-D Acoustics Goniometer (courtesy David T. Bradley)

We’re currently assisting David T. Bradley at Vassar College with his research into acoustic scattering and will be sharing some of the process and results of that research here on our blog.  This collaboration came about after David saw some of the visualizations (1,2) we produced while trying to simulate the behavior of sound with ray-tracing.  It turned out that David and his team were building a 3D acoustic goniometer for physically testing acoustic diffusion from surfaces(more about that later).

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Our role has been to generate a set of diffusive surfaces for testing.  The surface geometry is composed of repeating units that are derived from a pyramid, a common diffuser shape, and David specified a set of parameters to vary: length and width of the pyramids, depth, corner lift pattern, and the distribution pattern.

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At this point, we’ve generated digital versions of 14 surfaces that represent a variety of testing combinations and have also milled out a 24″ diameter physical version of each surface. The next step is for us to run each of the surfaces through our ray-tracing definition and the Vassar team will start analyzing the physical surfaces over the course of the summer.