Measurement of Sound Transmission Loss Properties in Single Multi-layered Systems - A Comparative Study between Two-room and Standing Wave Tube Techniques

摘要

Several methods have been established to measure the normal incidence transmission loss of noise control materials using the standing wave tube. In the automotive NVH field, multi-layered systems are commonplace, for example in the interaction between the traditional mass-decoupler dash insulator and the front dash sheet metal. Most of the sound transmission loss studies utilizing the standing wave tube have so far been focused on single layer systems with only a limited number of studies on multi-layered systems. Therefore there is only some degree of information on the correlation between this said method and the more widely accepted two-room methods of determining sound transmission properties in these systems. The paper details an empirical study using a four-microphone standing wave tube using the transfer matrix method and a couple of methods utilizing the traditional hemi-anechoic and reverberant room set up, including one using sound pressure technique and the other using sound intensity technique. The range of materials in the study includes porous and barrier materials in single and multi-layered system configurations. It is found that the material sound transmission loss ranking is generally consistent between the two-room methods using SAE J1400 and ISO 15186 and the standing wave tube method. However when the samples are coupled with a steel plate, there are resonance conditions which makes ranking the performance difficult. Also no consistent difference between the results of the two-room methods and the standing wave method is found, which makes correlating the data between the different methods difficult.