Technical note: Measuring system for qualification tests of free-field rooms

Free-field rooms need to be assessed with respect to acoustic quality as described in the relevant standards by sound pressure level decay tests that are compared to the expected decay of 6 dB per doubling of distance from the source. These tests are time consuming, as the microphone has to be moved along straight paths while recording the sound levels for each frequency. For this purpose, a new measuring system is described which accelerates the test procedure considerably with the aid of a self-propelled microphone positioning system and a computerized positioning and data analysis system.