Boundary element method for the acoustic characterization of a machine in bounded noisy environment

Abstract

In this article, a boundary element method is used to recover free field conditions from noisy bounded space situations. The proposed approach is based on the Helmholtz integral formulation. The method requires the knowledge of double layer pressure fields on two parallel closed surfaces surrounding the source. First, the outgoing and ingoing pressure field are separated using Helmholtz integral. Then, the incident field scattered by the tested source is subtracted from the outgoing field to recover the pressure field which would have been radiated in free space. To simplify the process, rigid body approximation for the source is used. The method is numerically tested in the following conditions: the chosen sound source is the upper spherical cap of a rigid sphere, the source is located at the center of a rigid spherical cavity, and a monopole secondary source is added to blur the primary pressure field. Simulations give good results for ka up to 5 when the discretization of the surfaces is sufficient.

Underwater moving noise source identification based on hybrid near-field acoustical holography

“…The boundary element method using a double layer [4] was proposed to overcome the restriction on the shapes of measurement surfaces. In order to overcome the problem of the truncation effect and wrap-around errors when the measurement aperture is not large enough in the classical NAH technique, the statistically optimized nearfield acoustical holography (SONAH) has been proposed [5,6].…”

Experimental feasibility of in-duct sound source reconstruction

“…A methodology based on the Green's representation of the pressure field has been proposed by Langrenne et al [7] to extract the outgoing radiated component from the measured acoustic pressure generated by a machine in an enclosure. It could be well suited for the IBEM localisation of the most vibrating parts of a machine.…”

The use of equivalent source models for reduced order simulation in room acoustics

“…In that work, it was shown that the room component of the total sound field, i.e. the sum of the incoming and scattering parts as in the usual terminology [18], can be approximated by radiation from a distribution of equivalent sources, monopoles in that case. Bi and Bolton's main concern was, however, to identify the free-space component of a source's radiation in a reverberant environment.…”