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The use of acoustic cavity fillers to prevent the propagation of air borne and structure borne noise, water and dust into the interior spaces of vehicle structures has been in practice for many years. Various technologies are available to OEMs to provide sealing that will prevent water and dust penetration, maximize performance of vehicle HVAC systems, and minimize the propagation of noise into a vehicle under operating conditions. The current state of the application of these technologies in the automotive, medium duty and heavy duty truck markets will be reviewed. Comparisons will be drawn between two categories of cavity fillers: pre-formed heat reactive expandable parts; and bulk applied chemically reacting polyurethane foam. Typical OEM material requirements will be discussed for these technologies. The pros and cons of these competing technologies, as well as their acoustic performance applied to a full vehicle will be considered.

Over the course of the past 19 years, the Sound Insertion Loss test method has become an accepted method for rank-ordering the acoustic performance of automotive Body-in-White cavity fillers by some OEMs in the United States. In some cases Insertion Loss data is required for a cavity filler material to be approved for use in a particular manufacturer's vehicles. In 2010, a formal SAE Insertion Loss test specification was created, SAE Technical Standard J2846. To gain an improved understanding of the variation inherent to the SAE J2846 Insertion Loss test method, a Gage Repeatability and Reproducibility (Gage R&R) analysis was performed. Gage R&R is a statistical tool used to measure the variation in a measurement system due to repeatability (error due to equipment variation) and reproducibility (error due to operator variation). The Gage R&R procedure followed for this paper can be found in the Measurement Systems Analysis Manual published by the Automotive Industry Action Group.

The use of acoustic cavity fillers or “baffles” to prevent the propagation of air borne and structure borne noise, water and dust into the interior spaces of vehicle structures has been in practice for many years. Continuous development of new OEM requirements has pushed the state of the art concerning the design and functionality of these cavity sealing systems. Various technologies are available to OEMs to provide sealing that will prevent water and dust penetration, maximize performance of vehicle HVAC systems, and minimize the propagation of noise from the body structure into the interior compartment under operating conditions.