Feasibility of In situ vehicle level transmission loss measurement to guide dash pass through grommet selections

Noise transmission through the vehicle dash panel plays a critical role in isolating passengers from noise sources within the motor bay of the vehicle. Grommets containing electrical harness routing as well as HVAC lines are examples of dash panel pass throughs that should be selected with care. Acoustic performance of these components is generally characterized in terms of measured quantities such as noise reduction (NR), sound transmission loss (STL), and Insertion Loss (IL). These measurements need to be carried out as per SAE or ASTM standards in appropriate anechoic or reverberant chambers as this is important for consistency. This work explores an in-situ vehicle measurement setup utilizing a repurposed vehicle cabin designed to serve as an anechoic chamber with its frunk acting as a reverberant chamber. This in-situ setup method is then compared to results following standards to discuss the differences in results. The data is studied to understand if there are any advantages to an in-situ measurement setup that might make it an alternative option to make directionally correct decisions regarding dash pass through selections.