Surface contributions to scattered sound power using non-negative intensity

Abstract

Non-negative intensity is used to identify the surface areas of a structure that contributes to the scattered sound power. In the acoustic near field, the scattered sound power is predicted using non-negative intensity, as well as the scattered acoustic intensity integrated directly over the scatterer's surface area. In the acoustic far field, the scattered acoustic intensity and the scattered sound power are evaluated for three different receiver surface areas, corresponding to a sphere representing a far-field area that fully circumscribes the scatterer, and two hemispherical surfaces that correspond to partial far-field areas that do not fully circumscribe the scatterer. Back-calculated non-negative intensity that defines the sound scattered from the full or partial far-field receiver surface areas is also calculated and compared to the non-negative intensity obtained directly from the surface of the scatterer. To illustrate the numerical technique, the scattered acoustic intensity and scattered sound power of a rigid sphere, a rigid cylinder, and a rigid hemispherical shell are examined.

Sound radiation and non-negative intensity of a metaplate consisting of an acoustic black hole plus local resonators

“…By introducing a discrete radiation model and an associated resistance matrix, the sound power level and radiation efficiency of the MMABH plate can be computed, following the steps in [22,61]. Finally, to determine which regions of the MMABH surface are responsible for the far-field sound radiation, we will resort to non-negative intensity (NNI) [62][63][64][65] as an alternative to supersonic intensity analysis [22,66,67] because of ease of implementation and slightly better performance at low frequecnies [68]. The paper is organized as follows.…”

Vibroacoustic subtractive modeling using a reverse condensed transfer function approach

“…For the purposes of validation, the approach proposed is compared with a reference calculation on an academic test case consisting of the scattering of an acoustic plane wave by a rigid sphere in an infinite water medium. This test case has been chosen because it has been deeply studied in the past (see for instance in [36][37][38]) and constitutes a reference for the study of the acoustic scattering by naval structures. Moreover, in the future, it could be easily upgraded to study the scattering of spheres coated by a soft rubber material [39,40].…”

Non-negative intensity for planar structures under stochastic excitation

“…It was shown that the results obtained using the useful intensity were not strictly the same as those obtained using the SSI. The NNI based on the BEM was also employed to identify the surface areas of a rigid sphere and a rigid cylinder that contributes to the scattered sound power [12]. The same technique was applied to localize the surface areas of vibrating structure to radiated sound power [13; 14].…”