CLEAN Based on Spatial Source Coherence

Sijtsma, Pieter

doi:10.1260/147547207783359459

Cited by 404 publications

(161 citation statements)

References 10 publications

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“…This lead to a total of 1000 blocks. Then, the cross spectral matrices were further processed by removing the main diagonal and applying the CLEAN-SC algorithm developed by Sijtsma [42]. The algorithm was used on a fully three-dimensional source region with dimensions of 0.6 m (chordwise direction) × 0.6 m (spanwise direction) × 0.4 m (vertical direction).…”

Section: Microphone Array and Data Processingmentioning

confidence: 99%

Experimental Study of Airfoil Leading Edge Combs for Turbulence Interaction Noise Reduction

2020

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The interaction of a turbulent flow with the leading edge of a blade is a main noise source mechanism for fans and wind turbines. Motivated by the silent flight of owls, the present paper describes an experimental study performed to explore the noise-reducing effect of comb-like extensions, which are fixed to the leading edge of a low-speed airfoil. The measurements took place in an aeroacoustic wind tunnel using the microphone array technique, while the aerodynamic performance of the modified airfoils was captured simultaneously. It was found that the comb structures lead to a noise reduction at low frequencies, while the noise at high frequencies slightly increases. The most likely reasons for this frequency shift are that the teeth of the combs break up large incoming turbulent eddies into smaller ones or that they shift turbulent eddies away from the airfoil surface, thereby reducing pressure fluctuations acting on the airfoil. The aerodynamic performance does not change significantly.

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Section: Microphone Array and Data Processingmentioning

confidence: 99%

Experimental Study of Airfoil Leading Edge Combs for Turbulence Interaction Noise Reduction

2020

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“…The resulting microphone auto spectra and cross spectra were averaged to yield the cross spectral matrix. This matrix was further processed using the CLEAN-SC deconvolution beamforming algorithm Sijtsma (2007), which was applied to a two-dimensional focus grid parallel to the array and aligned with the aerofoil. The grid has a streamwise extent of 0.5 m, a spanwise extent of 0.4 m and an increment of 0.005 m. The outcome of the beamforming algorithm is a two-dimensional map of noise source contributions from each grid point, a so-called sound map.…”

Section: Experimental Arrangementmentioning

confidence: 99%

An aeroacoustic investigation into the effect of self-oscillating trailing edge flaplets

Talboys

Geyer

Brücker

2019

Journal of Fluids and Structures

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The aeroacoustics of a NACA 0012 aerofoil with an array of self-oscillating flexible flaplets attached on the trailing edge has been investigated at low to moderate chord based Reynolds number (50,000 -350,000) and at geometric angles of attack from α g = 0 • -20 • . When the aerofoil is untripped, tonal peaks are observed on the baseline aerofoil. When the passive flaplets are attached to the pressure side of the aerofoil, the tonal peak is removed. If the flaplets are then placed on the suction side, the tonal peak is reduced, but not removed. It is therefore hypothesised that the flaplets on the pressure side modifies the laminar separation bubble situated on the pressure side of the aerofoil, a key mechanism for tonal noise. Throughout all cases, both tripped and untripped, a low frequency (0.1 kHz -0.6 kHz) noise reduction and a slight increase at higher frequencies (>2 kHz) is seen. This gives an average overall sound pressure level (OSPL) reduction of 1.5 -2 dB for the flaplets affixed to the pressure side. The cases where the tonal noise component is removed an OSPL reduction of up to 20 dB can be seen.

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“…It should be noted however, that since VRAM uses a frequency-domain beamforming formulation, a multitude of deconvolution methods can be applied there to enhance the beamforming map, e.g. CLEAN-SC [23]. Comparison between some methods can be found in [16].…”

Section: Beamforming Resultsmentioning

confidence: 99%

Comparison of the Rotating Source Identifier and the Virtual Rotating Array Method

Tóth

Vad

Kotán

2018

Period. Polytech. Mech. Eng.

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The aim of this paper is to present two acoustic beamforming methods developed for rotating sources, namely the Rotating Source Identifier (ROSI) and the Virtual Rotating Array method (VRAM). These were applied onto a series of simulated test cases, and their behaviour was analysed. Both methods were able to localise the source reliably. However, the source strength was found to depend on the number or microphones when VRAM was applied. This phenomenon was quantified and an approximate formula was given providing the minimum number of microphones required to reach a certain amplitude error. Beamwidth and side lobe suppression were found to agree between the two methods, meaning that the way rotation is handled does not significantly affect the point spread functions. The computational cost of ROSI was two to three orders of magnitude higher than that of VRAM. The results show that both methods are applicable for the beamforming analysis of rotating sound sources. However, in case of VRAM, the number of microphones has to be chosen carefully to obtain reliable amplitude results.

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CLEAN Based on Spatial Source Coherence

Cited by 404 publications

References 10 publications

Experimental Study of Airfoil Leading Edge Combs for Turbulence Interaction Noise Reduction

Experimental Study of Airfoil Leading Edge Combs for Turbulence Interaction Noise Reduction

An aeroacoustic investigation into the effect of self-oscillating trailing edge flaplets

Comparison of the Rotating Source Identifier and the Virtual Rotating Array Method

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