Acoustical Visualization of Aeroacoustic Noise Sources

To perform effective noise control, it is essential
that the detailed character of the noise source be
well understood. Near-field Acoustical Holography
(NAH) is a powerful tool for visualizing noise
sources and thus for identifying the detailed nature
of a source. NAH has been applied most often for
visualizing structure-borne and machinery noise
sources. In this book, it is shown how NAH can be
applied with equal success to aeroacoustic sources. A
detailed development of multireference NAH is
provided to allow the use of a scanning microphone
array. Also, methods for compensating for source
nonstationarity and for extrapolating sound fields
beyond the measurement aperture to improve the
accuracy of the source imaging are described.
Experimental results are given
for a ducted fan and for a free jet, and it is shown,
for example, that nearfield measurements allow the
accurate prediction of a source s farfield
directivity. The analysis presented in this book will
help scientists and engineers concerned with
visualizing aeroacoustic sources, in particular, and
more generally, any practical machinery noise
sources that comprise several
uncorrelated or partially correlated subsources.

Autorentext

Moohyung Lee: Earned his degrees in Mechanical Engineering. B.S.and M.S. from Seoul National University, Korea, and Ph.D. fromPurdue University, USA. Worked for Hyundai Motor Company ResearchCenter. Postdoctoral Researcher at the Ray W. HerrickLaboratories, Purdue University. Research on Acoustics,Vibration, and Signal Processing.

Klappentext

To perform effective noise control, it is essentialthat the detailed character of the noise source bewell understood. Near-field Acoustical Holography(NAH) is a powerful tool for visualizing noisesources and thus for identifying the detailed natureof a source. NAH has been applied most often forvisualizing structure-borne and machinery noisesources. In this book, it is shown how NAH can beapplied with equal success to aeroacoustic sources. Adetailed development of multireference NAH isprovided to allow the use of a scanning microphonearray. Also, methods for compensating for sourcenonstationarity and for extrapolating sound fieldsbeyond the measurement aperture to improve theaccuracy of the source imaging are described.Experimental results are givenfor a ducted fan and for a free jet, and it is shown,for example, that nearfield measurements allow theaccurate prediction of a source's farfielddirectivity. The analysis presented in this book willhelp scientists and engineers concerned withvisualizing aeroacoustic sources, in particular, andmore generally, any practical machinery noisesources that comprise severaluncorrelated or partially correlated subsources.