The Reflection Canceller - Phased Array Measurements in a Reverberating Environment

Guidati, Sandro; Bräuer, Christian; Wagner, S.

doi:10.2514/6.2002-2462

Cited by 21 publications

(13 citation statements)

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“…The choice of the source model is based on the fact that an extended sound source may only be viewed as an equivalence class between source functions radiating the same pressure field on a phased microphone array. In many (19)…”

Section: Spectral Estimation Methods (Sem)mentioning

confidence: 99%

“…In general, measurements with phased microphone arrays provide certain advantages with respect to measurements with individual microphones when performing acoustic measurements. For experiments in wind tunnels with openand closed-test sections, as well as in engine test cells, the background noise suppression capability of the source localization algorithms is very useful [1,[16][17][18], as well as the removal of reflections from the walls [19,20]. Beamforming can also be applied to moving objects, such as flying aircraft or rotating blades, provided that the motion of the source is tracked accurately [1].…”

Section: Historical Backgroundmentioning

confidence: 99%

“…A more radical solution for the TBL issues is to replace the wind-tunnel walls by Kevlar sheets, as in the stability tunnel of the Virginia Polytechnic Institute and State University [51]. In addition, acoustic measurements are hampered by reflections by the test section walls [19,20]. In general, acoustic measurements in closed-test sections are dominated by high noise levels, either due to the TBL pressure fluctuations or due to the noise from the windtunnel circuit.…”

Section: Closed-test Sectionsmentioning

confidence: 99%

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A review of acoustic imaging methods using phased microphone arrays

et al. 2019

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Phased microphone arrays have become a well-established tool for performing aeroacoustic measurements in wind tunnels (both open-jet and closed-section), flying aircraft, and engine test beds. This paper provides a review of the most wellknown and state-of-the-art acoustic imaging methods and recommendations on when to use them. Several exemplary results showing the performance of most methods in aeroacoustic applications are included. This manuscript provides a general introduction to aeroacoustic measurements for non-experienced microphone-array users as well as a broad overview for general aeroacoustic experts.

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Section: Spectral Estimation Methods (Sem)mentioning

confidence: 99%

Section: Historical Backgroundmentioning

confidence: 99%

Section: Closed-test Sectionsmentioning

confidence: 99%

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A review of acoustic imaging methods using phased microphone arrays

et al. 2019

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“…In order to effectively eliminate the influence of interference acoustic source, foreign and domestic scholars have made a lot of efforts. First, the "Reflection Canceller" technique, proposed by Guidati et al, is discussed, in which the mirror source determined by the reflection number of the acoustic source is added to the transmission model according to the mirror image principle, modified steering vectors are achieved to attenuate the impact of reflection [12]. A correction technique similar to the inverse method of Nelson is discussed, that keep the steering vector of the acoustic sources invariant and minimize the array output from the mirror source direction, so as to improve the sound source identification ability [13,14].…”

Section: Introductionmentioning

confidence: 99%

A new beamforming microphones array with acoustic insulation baffle

Shen¹,

Chu²,

Yang³

et al. 2017

J. vibroeng.

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To eliminate the influence of the interference acoustic source behind the array on the source identification performance, some modifications on the traditional single-layer beamforming microphone array are made, a new array with acoustic insulation baffle in the microphone plane is given out to suppress the influence of interference acoustic source. Simulation and verification results show that, with the presence of the interference acoustic source in the rear of traditional planar array, the acoustic source position and amplitude deviations are larger and it indicates that the interference acoustic source seriously affects the identification performance of target acoustic source. Compared to the performance of traditional planar array, the new microphone array with acoustic insulation baffle can effectively eliminate the influence of interference acoustic source behind the array and improve the accuracy of the location and amplitude of the target acoustic source. The experiment verifies the correctness of the simulation conclusions and the applicability of the modified microphone array in the cabin of automotive and aircraft and other narrow space.

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“…Carryingout also acoustic measurements in such facilities still remains a challenge yet, in particular due to unfavorable signal-to-noise ratios and to acoustic reflections in the test section. Given the interest of performing reliable acoustic measurements in aerodynamic wind tunnels, many efforts have been made for years to reduce the background noise in closed test sections 1, 2, 3 , to improve inflow acoustic measurements 4,5 and to develop data dereverberation techniques 6,7,8 . In particular, beamforming techniques based on the free-field Green's function may be able to provide noise source levels in reverberating test sections 9,10,11,12 .…”

Section: Introductionmentioning

confidence: 99%

2D high-lift airfoil noise measurements in an aerodynamic wind tunnel

Bahr¹,

Humphreys²,

Ernst³

et al. 2015

21st AIAA/CEAS Aeroacoustics Conference

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In the frame of the common project LEISA2 between ONERA and DLR, a 2D high-lift airfoil model of DLR was tested both in the ONERA's F2 aerodynamic wind tunnel and in the DLR's AWB anechoic wind tunnel. A large aeroacoustic database was collected. The present paper is concerned with the assessment of acoustic data in F2. The question of performing accurate noise level measurements in spite of the acoustic reflections in the test section is adressed in particular. The measurement technique relies on beamforming methodologies. The noise sources on the airfoil are firstly analyzed with the conventional beamforming technique, based on the free-field Green's function. A deconvolution algorithm is then applied to determine the acoustic level of the sources. To assess the results in F2, the deconvolved noise source levels are finally compared with noise spectra measurements in AWB. High-amplitude tones are observed and the corresponding noise sources are identified on the slat. The tone levels are imperfectly recovered yet. On the other hand, broadband noise levels are deemed in fair agreement between F2 and AWB. The broadband noise sources are identified both on the slat and the flap.f frequency C P static pressure coeff.: C P = P −P∞ 0.5ρ∞U 2 ∞ P local static pressure α F2 angle of incidence in F2 P ∞ static pressure at infinity α AWB angle of incidence in AWB U ∞ mean velocity at infinity ∆ spatial resolution of the scanning points ρ ∞ mean mass density at infinity

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The Reflection Canceller - Phased Array Measurements in a Reverberating Environment

Cited by 21 publications

References 0 publications

A review of acoustic imaging methods using phased microphone arrays

A review of acoustic imaging methods using phased microphone arrays

A new beamforming microphones array with acoustic insulation baffle

2D high-lift airfoil noise measurements in an aerodynamic wind tunnel

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