Abstract:

The method proposed is an option to the one described by ISO-140, which needs two reverberant chambers. It consists of a duct 3 m long with a cutoff frequency around 1300 Hz, with a loudspeaker at one end and an anechoic termination at the other. The sample is placed 1 m from the loudspeaker and two microphones are placed around 500 mm from the sample, the first between the loudspeaker and the sample and the second between the sample and the anechoic termination. An impulse is generated and captured at microphone 1 as the incident pulse at the sample and at microphone 2 as the transmitted pulse through the sample. The impulse size is controlled in order to have enough energy in the frequency range desired and not to be too long to mix with the pulse reflected by the sample. In the frequency domain, the energy difference between the signals is compared with the mass law. The ultimate goal of this research is achieving a simple technique for evaluation of transmission loss in multilayered partitions.