1 INTERIOR FOURIER NEAR-FIELD ACOUSTICAL HOLOGRAPHY USING ENERGY DENSITY

Near-field acoustical holography (NAH) is used to reconstruct three-dimensional acoustic fields from a two-dimensional planar measurement. During previous work at BYU, a method has been developed called energy-based near-field acoustical holography (ENAH), which reduced the number of needed measurements by 75%. Other recent advances have expanded the theory to interior spaces where multiple sources and/or reflections are present. This paper presents a new method for reconstructing interior acoustic parameters using Fourier NAH and a single plane of energy density measurements. Energy density is measured using a six-microphone array. First, the probe measurements are used to create a Hermite surface pressure interpolation on two separate planes. These two planes are used to approximate the normal particle velocity as well as to separate the incoming and outgoing waves using the spatial Fourier-transform method. Once separated, traditional Fourier NAH is used to reconstruct the pressure and normal particle velocity at any point in space. Analytical and experimental results are shown and compared to exterior Fourier NAH approximations. Other drawbacks and benefits are discussed. I