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Paper: Development of an Acoustically Rated Electrical Flush Box using Sound Intensity Measurement

Richard Latimer


The addition of electrical service penetrations in acoustically rated walls, is well known to reduce the walls acoustic performance. Previous testing has shown, there is a significant decrease in performance in mid to high frequencies. Typically, flush boxes are attached to the partition framing and a hole is cut out in the partition linings to mount a face plate, such as electrical plugs, light switches etc. Currently, there is no appropriate acoustic testing available for acoustic flush boxes on the market in New Zealand. Canterbury Acoustic Testing Services (CATS) has developed a flush box that does not reduce the overall performance of a tested STC 54 wall, either as a single, or back to back installation. Sound intensity measurements were taken in accordance with ISO 15186-1:2000 Acoustics — Measurement of sound insulation in buildings and of building elements using sound intensity — Part 1: Laboratory measurements. The test sample was measured using the discrete measurement position method, as described in ISO 15186-1, in a 100 mm grid pattern, using 10 second point measurements. Composite transmission loss calculations have shown that, there is no reduction in the single number rating of up to a STC 62 wall, using the newly developed acoustic flush box. 

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