Rotating microphones and MLS in building acoustics

摘要

The influence is investigated of the use of rotating microphones in room and building acoustics on measurements with pseudo random noise, in particular with maximum length sequences (MLS). With the assumption of a diffuse sound field, two operating modes can be distinguished: operation with and without synchronization between the length of the noise sequence and the cycle time of the microphone. Analytical expressions for the spectrum of the sound pressure level signal and for the decaying impulse response are derived. As the system is no longer time invariant, signal reduction and disturbance by additional noise that cannot be properly back transformed are observed. The theoretical results are compared with experiments in a reverberation room. [References: 14]