AES Section Meeting Reports

Pacific Northwest - January 8, 2020

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The PNW Section began the new decade with a presentation by Ron Sauro of NWAA Labs on developments in architectural acoustics. Although some would say the field is mature, Ron's research shows many familiar acoustic formulas are not as accurate as thought. The meeting, held at DigiPen Institute of Technology in Redmond, WA, drew some 36 attendees.

Ron started with an in-depth biography, including colorful times playing music, serving in the military, work at NASA, earning accelerated technical degrees, and becoming involved with the EASE acoustic software development.

Ron's NWAA Labs is an advanced acoustic test facility, built in a never-quite-finished nuclear power plant in Elma, WA. Massive structure and huge spaces make his test facility among the most versatile - and quietest (non-anechoic) - in the world. For the past decade, his numerous tests of acoustic materials and properties has shown that many of the classic formulas for predicting acoustic performance of materials and construction are outdated and he has the numbers to prove it. A photo tour of the facilities showed the large arced array of microphones for tests including diffusion and scattering, and the 737 cubic-meter reverb room used for transmission loss and absorption tests.

He discussed many issues with transmission loss test mounts and tests for acoustic absorption coefficients, diffusion, and transmission loss. These were shown to be less accurate than his research numbers indicated. Diffraction and edge effects were also covered. His feeling is that the existing methods for room absorption calculations are inaccurate, and he proposes a different formula for a constant. Several "myths" about absorption were also dispelled, such as absorber arrangement, perimeter and spacing, and wall mounting of panels.

Diffusion and scattering testing also came under fire - it is a complicated effect, so the traditional information is lacking. He showed several massive 3-D particle modelling animations of diffusion tests, done by Jim DeGrandis of Acoustics First!

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AES - Audio Engineering Society