Determining Sound Transmission Loss of SAE J1400 Control Sample

SAE acoustics materials committee published updates of SAE J1400 Standard - Laboratory Measurement of the Airborne Sound Barrier Performance of Flat Materials and Assemblies in 2017. In the standard, a control sample is defined with a specific construction to determine the suitability of the test suite. A set of measured sound transmission loss data of the control sample are included in the published updated standard. Autoneum North America Acoustics Laboratory constructed a control sample based on the design in the standard. Sound transmission loss (STL) measurement of this control sample was performed and results are consistent with published data below 2000 Hz. Above 2000 Hz, STL results are above published limits. Sound intensity measurement and flanking noise paths measurements confirmed the measured STL values of the control sample. Furthermore, simulation results based on transfer matrix method indicate that the control sample STL could be higher than the data published in the J1400 standard at high frequencies. This paper discusses the STL measurements of the control sample step by step, in an attempt to investigate the “true” value of sound transmission loss for the control sample.