Inverse and reciprocity methods for experimental determination of radiation modes.

Experimental methods are presented for the problem of finding the vibration patterns of a structure that radi-ate sound most efficiently. These vibration patterns, the so-called radiation modes, diagonalize the acoustic radiation operator and therefore radiate independently. The methods that are considered are reciprocity methods, inverse methods and a combination of these methods. The reciprocity technique is applied to the problem of finding the radiation modes for velocity sensing that contribute to the potential energy in an enclosure. Measured results agree with simulated results. Using an inverse technique, it is shown that the radiation modes for sensing with an array of piezoelectric patch sensors can be found. Improved results can be obtained by combining the inverse method with a reciprocal technique for measuring some of the transfer functions.