Rapid In-Place Measurements of Multichannel Venues
It is often useful to have transfer-function measurements of large venues with an audience present. This precludes multiple chirps or other long-duration signals from being used. This paper studies the use of simultaneous, multiple ‘orthogonal’ maximum-length sequences applied to the loudspeakers, captured by a number of microphones at selected listening positions. Such MLS signals last only a few seconds and are noise-like, being minimally disruptive to an audience, yet they allow full transfer-function system identification between each loudspeaker and microphone. The main detractor of the method is that the effective noise level is high. This paper studies implementation issues, and assesses the S/N of such measurements. It turns out that exciting each loudspeaker separately is usually better than simultaneous excitation, except in special circumstances. An example is shown for the simultaneous measurement of two loudspeakers in a room with two microphones.
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