Alternative Sample Mounting Techniques for Small Reverberant Chambers

This paper reviews an alternative approach for mounting flat absorptive samples in small reverberant chambers, which improves the accuracy of random incidence sound absorption measurements.

A square recessed cavity is proposed, which allows flat test samples to be flush mounted to the floor of the chamber. This design feature eliminates acoustical measurement errors caused by diffraction effects at the edges of the samples, which are particularly pronounced in small reverberant chambers.

Random incidence sound absorption data are presented for fibrous and cellular flat acoustical insulation samples placed on the floor, and compared with data produced when those same samples were mounted using the flush mount system in a small reverberant chamber. The sample edge diffraction effects are quantified over a frequency range of 250 - 10,000 Hz.