Abstract
When measuring the sound absorption coefficient according to ISO 354:2003, the standard commonly requires the use of a reflective frame around the perimeter of the test specimen, to keep the edges from absorbing sound. Logically, this is most important at high and medium frequencies, but previous studies have shown a significant impact also at lower frequencies. At this end of the spectrum, the frame seems to have a positive effect on the measurement results – an effect that persists even when the test specimen is only partially covered by a frame. To get closer to the cause of this phenomenon, reverberation room measurements have been carried out on a partially framed test specimen. Several different configurations of a partial frame have been tested, with a view to observe whether the position of the partial frame relative to the test specimen is of any importance to the measurement results. The results from these measurements are presented and discussed in this paper.