Modal Deconvolution Method in a Finite Circular Duct, using Flush-mounted Microphones

Fauqueux, Sandrine; Davy, Renaud

doi:10.2514/6.2018-3927

Cited by 12 publications

(16 citation statements)

References 11 publications

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“…The analytical model of the Fourier transform of the acoustic pressure field being defined, either under uniform or shear flow, we can now briefly introduce our deconvolution method, called ARMADA (Azimuthal and Radial Modal Analysis for in-Duct Acoustics). See [1] for more details. We consider an antenna composed by N flush-mounted microphones of coordinates (x i , R, θ i ) i=1..N in the coordinate system represented in Fig.…”

Section: Armada Deconvolution Methodsmentioning

confidence: 99%

“…None regularization scheme is currently used. In Liebherr Aerospace's facility, the deconvolution method is applied under the correlated modes assumption, as reflections may occur at the end of the duct that imply correlation between downstram and upstream modes at least [1].…”

Section: Armada Deconvolution Methodsmentioning

confidence: 99%

“…The second one is composed of two rings and a linear array, each part being discretized with a constant step. We use the numerical evaluation procedure presented in [1], §2, to determine the minimum amount of microphones and the space step of the linear array that enables a satisfying estimation of the modal content. For frequency greater or equal to 2000 Hz, only the second design gives good estimation results.…”

Section: Microphone Array Designmentioning

confidence: 99%

“…ONERA recently developed a modal deconvolution method, called ARMADA [1], based on the iterative minimization of the discrepancy, in the least-square sense, between flush-mounted microphone measurements and an analytical model that represents the propagation between the sources and the measurements positions. A rigid and infinite cylindrical or annular duct of constant radius subjects to a uniform and subsonic flow along the revolution axis of the duct is currently considered.…”

Section: Introductionmentioning

confidence: 99%

See 3 more Smart Citations

Duct modal detection tool to characterize the noise source generated by an air pump

Fauqueux¹,

Davy²,

Méry³

2019

25th AIAA/CEAS Aeroacoustics Conference

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Aircraft air conditioning system must be compliant with the Noise Regulations of every countries in which it will be operated. In the Clean Sky 2 project IDEAS, the system of interest is composed of an air pump, developped by Liebherr Aerospace, that generates low and mid-frequency noise that may be mitigated by the use of innovative acoustic liners. The aim of this study is to assess the level and modal content of the generated noise source in two industrial operating conditions. The modal detection solution proposed by ONERA leads to the post-treatments of measurements obtained by a flush-mounted microphone array located downstream of the diffuser. As microphones will be implemented in a hard-wall region of the duct, the modal basis characterizing the measured acoustic field does not depend on the lined walls, located in the diffuser area. The deconvolution method ARMADA leads to the minimization of the discrepancy, in the least-square sense, between measurements and an analytical model of the acoustic pressure field that propagates in cylindrical ducts. In the first part of this article, the analytical models in uniform and non-uniform flows are introduced, with underlying hypotheses. In the case of shear flow, the modal shapes are given by ONERA's MAMOUT code. Then, the deconvolution method is presented, considering that the modes are correlated, as wave reflections may occur at the end of Liebherr's bench. In the second part, the design of the IDEAS microphone array is defined, considering uniform flow only. Different sensor arrangements are compared. One design is retained and the associated estimation errors are assessed. In the third part, the impact of estimating modes under the uniform flow hypothesis despite the fact that shear flow occurs during measurements is evaluated. A potential misleading impact is highlighted at 3150 Hz on the m = 0 and n = 1 mode. Finally, the experimental setup is introduced and the analysis of the measurements performed in the facility without use of acoustic liners are detailed for two operating conditions.

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Section: Armada Deconvolution Methodsmentioning

confidence: 99%

Section: Armada Deconvolution Methodsmentioning

confidence: 99%

Section: Microphone Array Designmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 2 more Smart Citations

Duct modal detection tool to characterize the noise source generated by an air pump

Fauqueux¹,

Davy²,

Méry³

2019

25th AIAA/CEAS Aeroacoustics Conference

Self Cite

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“…A modal decomposition technique allows such a characterization of the acoustic eld structure (modes) inside a duct. A wide range of decomposition methods are already available, ranging from source localization techniques such as beamforming [7,8], singular values decomposition [9], deconvolution methods [10] and pseudo-inverse resolution of a linear problem. The foundation of the latter procedure was proposed by Åbom [11], who rst recognized that the two-microphone transfer function method by Chung and Blaser [12] could be extended to non plane wave modes.…”

Section: Introductionmentioning

confidence: 99%

Bayesian inference for modal identification in ducts with a shear flow

Roncen

Méry

Piot

2019

The Journal of the Acoustical Society of America

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An induct modal decomposition technique is described. The basis for the technique is to consider the decomposition as an inference problem. Using transfer function measurements at the duct walls, a Bayesian inference is conducted to evaluate the acoustic modal coecients in the presence of uncertainties. These uncertainties encompass model errors, microphone measurements error, and uncertainty on the ow prole. The formalism of the direct problem of modal decomposition in a ducted shear ow is rst developed. The case of a circular cross-section duct is then treated without and with a ow, using synthetic noisy signals for the inference problem.

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Aeroacoustics research in Europe: The CEAS-ASC report on 2018 highlights

Gely

Bennett

2019

Journal of Sound and Vibration

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The Council of European Aerospace Societies (CEAS) Aeroacoustics Specialists Committee (ASC) supports and promotes the interests of the scientific and industrial aeroacoustics community on an European scale and European aeronautics activities internationally. In this context, "aeroacoustics" encompasses all aerospace acoustics and related areas. Each year the committee highlights some of the research and development projects in Europe.This paper is a report on highlights of aeroacoustics research in Europe in 2018, compiled from information provided to the ASC of the CEAS. During 2018, a number of research programmes involving aeroacoustics were funded by the European Commission. Some of the highlights from these programmes are summarised in this article, as well as highlights from other programmes funded by national programmes or by industry. Furthermore, a concise summary of the CEAS-ASC workshop "Future Aircraft Design and Noise Impact" held in the Netherlands Aerospace Centre (NLR) Amsterdam in September 2018 is included in this report.Enquiries concerning all contributions should be addressed to the authors who are given at the end of each subsection.

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Modal Deconvolution Method in a Finite Circular Duct, using Flush-mounted Microphones

Cited by 12 publications

References 11 publications

Duct modal detection tool to characterize the noise source generated by an air pump

Duct modal detection tool to characterize the noise source generated by an air pump

Bayesian inference for modal identification in ducts with a shear flow

Aeroacoustics research in Europe: The CEAS-ASC report on 2018 highlights

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