Advances in nearfield acoustical holography (NAH) algorithms I. Green's functions
نویسندگان
چکیده
منابع مشابه
Session 1pSPa: Nearfield Acoustical Holography (NAH) Measurements and Applications 1pSPa4. Modified statistically optimized near-field acoustical holography for jet noise characterization
Near-field acoustical holography has been shown to be a useful tool for visualizing jet noise fields. It has been applied to a full-scale jet on an installed military aircraft with promising results, but the source characteristics in the extreme near field have been difficult to characterize because of the interference of acoustic reflections off the rigid reflecting plane beneath the jet. To p...
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The article describes the results of two methods: the Fresnel approximation and the convolution method used for the exact Rayleigh-Sommerfeld equation. Curves for the Fresnel approximation are shown as a function of flaw depth and number of sample points. Despite a violation of the fresnel condition, an image can be achieved without visible phase distortion. This and its limits are shown on syn...
متن کاملOn nearfield acoustic holography
Such functions u are called radiating solutions. Pressure measurements are taken by acoustical sensors located in a domain Ω0 inside or outside the cabin or on a surface Γ0 = ∂Ω0 . Our goal is to reconstruct u inside Ω, or the normal velocity v = ∂νu on Γ = ∂Ω, (ν is the unit exterior normal to ∂Ω). This is a mathematical model of the nearfield acoustic holography [W], [Wu]. H(m)(Ω) denotes the...
متن کاملA general radiation model for sound fields and nearfield acoustical holography in wedge propagation spaces.
In this work an expression for the solution of the Helmholtz equation for wedge spaces is derived. Such propagation spaces represent scenarios for many acoustical problems where a free field assumption is not eligible. The proposed sound field model is derived from the general solution of the wave equation in cylindrical coordinates, using sets of orthonormal basis functions. The latter are mod...
متن کاملOn the Use of Higher Order and Irregularly Shaped Boundary Elements in Nearfield Acoustical Holography
Nearfield acoustical holography (NAH) is used to find the regions of acoustic activity on the surface of a sound radiating object. One of the most general NAH approaches is the inverse frequency response function (IFRF) technique, since it imposes no limitations on the geometry of the radiating boundary. In the IFRF method acoustic measurements on a grid in the nearfield of the object are used ...
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ژورنال
عنوان ژورنال: The Journal of the Acoustical Society of America
سال: 1984
ISSN: 0001-4966
DOI: 10.1121/1.2021577