Transmission loss measurement of multilayered partitions in time domain

Abstract

Transmission loss through single-layered partitions depends on the superficial specific mass m of the material. A multilayered partition has, at each interface, an impedance jump that improves its transmission loss. Due to these characteristics, multilayered partitions can provide better sound insulation than a single-layered partition with the same thickness, being much lighter. In this work an experimental setup was built to study the transmission loss of a sample inside a duct. The partition is inserted between two sections of the duct and a pulse is generated at one side. The incident and the transmitted signals are captured by free-field microphones, and the time domain series, acquired with a two channel digital oscilloscope, provides the transmission loss. The impedance of the materials tested was found experimentally and compared with tables, when available. The experiment was performed in order to evaluate transmission loss in single-, double- and three-layered partitions. The experimental results were compared with numerical simulation using the software layer, developed in our laboratory, showing good agreement.