Sound transmission loss of orthotropic sandwich panelss
Lightweight orthotropic sandwich panels are used in aircraft floors. These panels have poor acoustic properties and transmit undesirable levels of noise into passenger cabins. To quantify acoustic behavior and to design noise control measures, we require a test facility and a design tool. The objective of this paper is to describe an experimental acoustic test facility, report the sound transmission loss (TL) measurements made on sandwich panels with different orthotropic cores, and compare the results of typical cases to predictions based on higher order sandwich panel theory (HSAPT).Get more news about Bh-sandwich Panel Series,you can vist our website!
To measure sound transmission loss of sandwich panels, a TL facility was constructed at USC's Composites Center in 2003 that allowed measurements at and above 630 Hz 1. Recently, modifications were made to the window that extended the lower frequency limit for reliable TL measurements to 315 Hz. The facility consists of a reverberant source room of 15 cubic meter volume with non-parallel walls, and a rectangular-shaped anechoic receiver room of 15 cubic meter volume. The test sample of size 1.067m by 1.067m occupies a window between the two chambers and a slat frame clamps the sample along the edges on the receiver room side. Sound power measurements made using sound intensity technique were used to calculate TL.
The facility was calibrated with a standard steel panel. Orthotropic sandwich panels selected for the tests were made of either Nomex honeycomb core or balsa core. The face sheets chosen were glass fiber - epoxy or polyester mats. The comparison of the experimental TL with the HSAPT based predictions showed good agreement in trend between the experiment and theory at most frequencies between 315 and 8000 Hz. The coincidence frequency also has good agreement and lies at ∼2000 Hz for both panels. The experimental facility, together with the higher-order theory based predictive tool, provides an essential framework to design passive noise control for honeycomb sandwich panels.