Prediction of radiated sound power from vibrating structures using the surface contribution method

A common measure for near-field acoustic energy of a vibrating structure is the acoustic intensity, which usually has positive and negative values that correspond to energy sources and sinks on the surface of the radiating structure. Sound from source and sink areas partially cancel each other and only a fraction of the near-field acoustic energy reaches the far-field. In this paper, an alternative method to identify the surface areas of a vibrating structure that contribute to the radiated sound power is described. The surface contributions of the structure are based on the acoustic radiation modes and are computed for all boundaries of the acoustic domain. In contrast to the sound intensity, the surface contributions are always positive and no cancellation effects exist. To illustrate the method, the radiated sound power from a resonator is presented.