A Desktop Procedure for Measuring the Transmission Loss of Automotive Door Seals 2017-01-1760
Due the increasing concern with the acoustic environment within automotive vehicles, there is an interest in measuring the acoustical properties of automotive door seals. These systems play an important role in blocking external noise sources, such as aerodynamic noise and tire noise, from entering the passenger compartment. Thus, it is important to be able to conveniently measure their acoustic performance. Previous methods of measuring the ability of seals to block sound required the use of either a reverberation chamber, or a wind tunnel with a special purpose chamber attached to it. That is, these methods required the use of large and expensive facilities. A simpler and more economical desktop procedure is thus needed to allow easy and fast acoustic measurement of automotive door seals. In the present work, a desktop, four-microphone, square cross-section standing wave tube was modified by the addition of a new sample holder to make it possible to measure the transmission loss of door seals under various states of compression. In this new procedure, the sample is clamped between a sliding piston and one wall of the standing wave tube. Since the clamp partially blocks the channel, thus impacting the measured transmission loss, a correction is necessary to determine the transmission loss of the seal by itself. Therefore, an initial set of measurements was performed to identify the correction factor required to adjust the measured transmission loss of the clamp plus seal to eliminate the contribution of the clamp itself. Once the accuracy of the correction procedure was verified, a number of typical door seals were tested at various degrees of compression. The transmission losses of the seals were generally in excess of 30 dB, and the transmission loss was found to increase significantly as the seals were compressed. The latter point, in particular, indicates that careful design of the seal mounting arrangements in the vehicle is crucial to ensuring their optimal performance.