Challenges in diagnosing noise and vibration problems using nearfield acoustical holography
Abstract:
This seminar gives an overview of Nearfield Acoustical Holography (NAH) technology and its development over the last three decades, with an emphasis on engineering applications by identifying root causes of sound radiation from a complex vibrating structure. Unlike traditional noise diagnostic approach, which yields a specific acoustic quantity at a specific location using a microphone, an intensity probe, an accelerometer or a laser vibrometer, NAH displays the entire sound field generated by a complex source in 3D space including visualization and quantification of source strengths on the source surface and their ranking. It is noted, however, that NAH does not deal with actual noise control, but rather with identifying the root causes and area where such efforts can yield the most benefits. Specific NAH implementation methodologies will be discussed, including original planar NAH using Fourier acoustics, Boundary Element Method based NAH, and Helmholtz Equation Least Squares (HELS) method based NAH. Comparisons of the advantages and disadvantages of NAH versus conventional intensity probe analysis and beamforming technique will be presented. Finally, actual examples of noise diagnoses using the HELS based NAH for automobiles, aircraft, and appliances such as vacuum cleaners, pumps, etc. will be demonstrated.
Applied Mathematics Seminar