Abstract

Acoustical-based imaging systems have found merit in determining the behavior of vibrating structures. This thesis focuses on the continued development of the nearfield acoustic holography (NAH) approach. Conventional NAH consists of first measuring the pressure field on a two-dimensional conformal surface and then propagating this data back to the vibrating structure to obtain information about the source, such as the normal velocity distribution. Recent work has been done which incorporates particle velocity information into the traditional NAH measurements to reduce the number of measurements required. This advancement has made NAH a more affordable tool for acoustical imaging and sound field characterization. It is proposed that the inclusion of velocity information into traditional NAH can further increase its usefulness. By propagating the velocity and pressure values independently and recombining them on the reconstruction surface, the pressure field and energy density fields can be predicted at any point in the sound field. It is also proposed that the same NAH measurement can be used to predict farfield directivity. The inclusion of velocity values into the NAH technique also provides a means for predicting energy density (ED) anywhere within the acoustic field. These two developments would allow a single NAH measurement to provide much more information about an acoustic source and its radiated sound field. Experimental testing shows that NAH is successful at predicting the shape of the resulting ED field and directivity pattern with some error in amplitude. The best performance of the technique is with a planer source resulting in an average amplitude error of 18.5% over the entire field.

Degree

MS

College and Department

Ira A. Fulton College of Engineering and Technology; Mechanical Engineering

Rights

http://lib.byu.edu/about/copyright/

Date Submitted

2009-07-09

Document Type

Thesis

Handle

http://hdl.lib.byu.edu/1877/etd3016

Keywords

nearfield acoustical holography, energy density, directivity

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