Active playback of acoustic quadraphonic sound events

The reconstruction into a cinema hall or a smaller room, of a sound event which has been previously recorded in a different acoustical environment is an interesting and still open acoustical problem. A new method for hi-fi multi-channel audio playback based on the general solution of the acoustical inverse problem is here proposed. This is implemented as a general feed-forward redundant control system where the number of acoustical signals to be reconstructed is greater than the number of the control signals feeding one or more loudspeakers working as active boundaries of the virtual playback room. This way an optimal and stable solution via a least square approach is obtained. This control system can be implemented even for complex configurations thanks to acoustic quadraphony: the application of sound intensimetry to audio technology recently developed within the IST-2-511316-IP European project denominated IP-RACINE. After a short explanation of the model theory, the experimental application to the simplest case of 1-D confined field is here presented and some experimentally obtained results are shown.