Numerical Investigation of the Transmission Loss of Seals and Slits for Airborne SEA Predictions

Seals and slits are often an important transmission path for vehicle interior noise at mid and high frequencies, and they are therefore often included in system level SEA models of interior noise. The transmission loss of seals and slits in such models is typically either measured experimentally or predicted using simple analytical models. The problem with the former is that it is expensive to investigate different design options using test; the problem with the latter is that simple analytical models often do not contain enough detail. The objective of this paper is therefore to investigate how much detail is needed in order to predict the transmission loss of typical slits and seals.

Typical door seals are not directly exposed to exterior and interior sound fields, but instead are inserted in complicated “channel” sections formed by the door and pillar or rail structures. This study is therefore divided in two parts. The first part focuses on the effect of the channel (a “slit” type aperture between two acoustic spaces). The acoustic performance of various slits is investigated using fast 3D numerical models based on the Hybrid FE-SEA method. The use of this method makes it possible to diagnose the parameters controlling the transmission loss of a slit or seal across a broader frequency range than is possible with standard numerical methods such as BEM.

The second part of the paper focuses on the transmission loss of the seal itself (with and without the presence of the channel). The sensitivity of the transmission loss to the deformation of the seal is also investigated (the deformation of the seal is predicted using a full non-linear deformation/contact analysis).