The use of steel coil springs is common in the building acoustics field. Steel coil springs are used in floating floors, isolated ceilings, and HVAC isolation. Products that use them are often considered to be "best in class" because of their low stiffness that can allow a spring-mass system to have a fundamental natural frequency of around 3 Hz. Unfortunately, this is an oversimplification of their performance. Steel coil springs have more complex modes that can degrade performance. These are often call surge frequencies. This paper will analyze airborne and impact sound transmission data and link features in the data to the surge and other modes of vibration. The modes of vibration will be confirmed by analytical calculation, experimental measurement and finite element modeling.
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