Nearfield acoustical holography for interior spaces

In this thesis the techniques of Nearfield Acoustical Holography (NAH), a method for predicting acoustic radiation based upon measured acoustical field data, were extended to apply to acoustical radiation in interior spaces. A separation of variables approach to the problem was formulated, which was shown to provide a uniform approach to the treatment of interior problems in separable geometries through the use of NAH, and that procedure was tested experimentally. The literature on NAH was reviewed in order to provide the frame of reference for the current work and to show the logical progression from the exterior problems investigated by previous authors by using NAH to the interior problem investigated here. Then, the current approach to the interior problem, based upon separation of variables, was developed. A numerical formulation of the interior NAH procedure suitable for processing on a computer with experimental data as the input was then developed. That numerical formulation was applied to experimental data collected in both controlled and practical interior spaces conforming to both Cartesian and cylindrical coordinate systems. The results of the experimental analysis showed that the techniques could be used to accurately predict the acoustic field and that the techniques developed in this work could be applied to practical problems outside of a controlled setting. The work presented in this thesis has a variety of interior acoustical applications, including automobile and aircraft cabins. Additionally, the results presented here for the separable coordinate systems that NAH applies to can be used to benchmark the accuracy and highlight the practical considerations that would be encountered in applying techniques similar to NAH, such as the inverse boundary element method, to interior acoustic problems in more complicated geometries