Velocity-Based Nearfield Acoustic Holography
Numerical investigations of nearfield acoustic holography in a contaminated acoustic field were performed. In this study, a baffled piston vibrating at low frequencies was chosen as the primary source. In addition, two types of disturbing sources were also considered. These sources were monopoles and plane waves propagating either perpendicularly or parallel to the hologram plane. Because pressure-based nearfield holography (PBNAH) was quite sensitive to the disturbing sources, a new method called velocity-based nearfield holography (VBNAH) was developed. The backpropagation images of the baffled piston obtained by using the VBNAH technique were compared to the images provided by the PBNAH technique. In the presence of the disturbing sources, VBNAH provided, in general, significantly better images than PBNAH. Errors caused by the disturbing sources depended on the type of those sources and their location with respect to the hologram plane.
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