Integration methods for distributed sound sources

Abstract

Most acoustic imaging methods assume the presence of point sound sources and, hence, may fail to correctly estimate the sound emissions of distributed sound sources, such as trailing-edge noise. In this contribution, three integration techniques are suggested to overcome this issue based on models considering a single point source, a line source, and several line sources, respectively. Two simulated benchmark cases featuring distributed sound sources are employed to compare the performance of these integration techniques with respect to other well-known acoustic imaging methods. The considered integration methods provide the best performance in retrieving the source levels and require short computation times. In addition, the negative effects of the presence of unwanted noise sources, such as corner sources in wind-tunnel measurements, can be eliminated. A sensitivity analysis shows that the integration technique based on a line source is robust with respect to the choice of the integration area (shape, position, and mesh fineness). This technique is applied to a trailing-edge-noise experiment in an open-jet wind tunnel featuring a NACA 0018 airfoil. The location and far-field noise emissions of the trailing-edge line source were calculated.

Experimental Investigation of Airfoil Turbulence-Impingement Noise Reduction Using Porous Treatment

“…The background noise corresponding to the configuration with the rod and without the airfoil has been recorded to be taken into account during the analysis of the results. The data have been post-processed with a Generalized Inverse Beamforming (GIBF) technique developed at VKI and validated through its application to an experimental [29,30] and a numerical [31] benchmark dataset. The isolation of the different noise sources that is possible to achieve with beamforming ended up being essential for the analysis of turbulence-impingement noise.…”

3D-printed Perforated Trailing Edges for Broadband Noise Abatement

“…Due to the background noise levels encountered in the anechoic chamber for the described testing conditions, and the lower resolution of the array at low f , the minimum reported f c is 500 Hz. The removal of acoustic sources other than broadband trailing edge noise is carried out applying source power integration [35] within -0.4 < Z/c < 0.4 and -0.6 < X/c < 0.4 (dashed rectangle in Fig. 5 (a) and (b)).…”

Analysis of nose landing gear noise comparing numerical computations, prediction models and flyover and wind-tunnel measurements

“…A standard shear layer correction, as outlined by Amiet [49], was applied. The beamforming results were integrated over a region of integration (ROI) covering the NLG position, following the approach of the Source Power Integration technique (SPI) [39,50]. The beamforming results were normalized by the integrated array response for a point source in the center of the ROI, also known as Point Spread Function (PSF).…”