MLS measurement system

The acoustics of a room is typically measured as a so-called room impulse response (RIR) from which various room acoustic parameters can be extracted. In relation to the introduction of 3D-sound, one operates with a binaural room impulse response (BRIR), which is measured via an artificial head and thus involves two channels. Subsequently, a BRIR can be used for auralization, where sound stored on a computer can be applied to the BRIR of a room. It will then appear as if the sound comes from a given position in that room. In order to measure BRIRs, a two-channel maximum length sequence (MLS) measurement system is being developed. MLS measurement systems have been known for some years and have gained wide popularity, especially due to their superior noise immunity. They have, however, the limitation that non-linearities and time-variances within the measurement object (e.g. in terms of local temperature changes in the room and mechanical non-linearities in the speaker) result in errors in the BRIR measured. For the measurement system, a special technique has been developed which utilizes averaging and constructs the measuring signal by combining different types of MLS signals. In effect the measuring error is minimized.