Capabilities of inverse scheme for acoustic source localization at low frequencies

Gombots, Stefan; Kaltenbacher, Barbara

doi:10.1051/aacus/2021034

Cited by 7 publications

(14 citation statements)

References 55 publications

(62 reference statements)

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“…The temperature was about 26°C, the relative humidity 30%, and the atmospheric pressure was 98 kPa during the calibration and measurement. The microphones were calibrated according to the procedure described in [44]. The EDF is mounted at a fixed location inside a measurement room.…”

Section: Operation Conditionmentioning

confidence: 99%

“…The acoustic properties of the facility limit the reliable experiments to frequencies above 300 Hz [45]. The room was characterized by reverberation time measurements in [5,44].…”

Section: Operation Conditionmentioning

confidence: 99%

“…The measurement concept followed the data processing presented in [44]. Prepolarised back-electret condenser microphones (Sennheiser KE 4-211-2) with windscreens recorded the acoustic signal.…”

Section: Operation Conditionmentioning

confidence: 99%

See 2 more Smart Citations

An Affordable Acoustic Measurement Campaign for Early Prototyping Applied to Electric Ducted Fan Units

Schoder¹,

Schmidt²,

Fürlinger³

et al. 2023

Preprint

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New innovative green concepts in electrified vertical take-off and landing vehicles currently emerge as a revolution to urban mobility going into the third dimension (vertically). The high population density of cities makes the market share highly attractive while posing an extraordinary challenge for community acceptance due to the increasing and possibly noisier commuter traffic. In addition to passenger transport, package deliveries to customers by drones may enter the market. The new challenges associated with this increasing transportation need in urban, rural and populated areas pose challenges for established companies and startups to deliver low-noise emission products. The article's objective is to revisit the benefits and drawbacks of an affordable acoustic measurement campaign focused on early prototyping. In the very early phase of product development, often considerably limited resources are available. With this in mind, the article discusses the sound power results using the enveloping surface method in a typically available low-reflection room with a reflecting floor according to DIN EN ISO 3744:2011-02. The method is applied to a subsonic electric ducted fan (EDF) unit of a 1:2 scaled electrified vertical take-off and landing vehicle. The results show that considerable information at low costs can be gained for the early prototyping stage, despite this easy-to-use, easy-to-realize, and not fine-tuned measurement setup. Furthermore, the limitations and improvements to a possible experimental setup are presented to discuss a potentially more ideal measurement environment. Measurements at discrete operating points and transient measurements across the total operating range were conducted to provide complete information on the EDF's acoustic behavior. The rotor-self noise and the rotor-stator interaction were identified as primary tonal sound sources, along with the highest broadband noise sources located on the rotor. Based on engineering experience, a first acoustic improvement treatment is also quantified with a sound power level reduction of 4dB(A). In conclusion, the presented method is a beneficial first measurement campaign to quantify the acoustic properties of an electric ducted fan unit at minimal resources in a reasonable time of several weeks when starting from scratch.

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Section: Operation Conditionmentioning

confidence: 99%

“…The acoustic properties of the facility limit the reliable experiments to frequencies above 300 Hz [45]. The room was characterized by reverberation time measurements in [5,44].…”

Section: Operation Conditionmentioning

confidence: 99%

See 1 more Smart Citation

An Affordable Acoustic Measurement Campaign for Early Prototyping Applied to Electric Ducted Fan Units

Schoder¹,

Schmidt²,

Fürlinger³

et al. 2023

Preprint

View full text Add to dashboard Cite

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“…Sound propagation models based on numerical simulation allow more complex geometrical setups. A source localization method using Finite Element simulation on two-and three-dimensional geometries is presented by Kaltenbacher, Kaltenbacher & Gombots in [26,15].…”

Section: Introductionmentioning

confidence: 99%

Uniqueness of an inverse source problem in experimental aeroacoustics

2020

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This paper is concerned with the mathematical analysis of experimental methods for the estimation of the power of an uncorrelated, extended aeroacoustic source from measurements of correlations of pressure fluctuations. We formulate a continuous, infinite dimensional model describing these experimental techniques based on the convected Helmholtz equation in R 3 or R 2 . As a main result we prove that an unknown, compactly supported source power function is uniquely determined by idealized, noise-free correlation measurements. Our framework further allows for a precise characterization of state-of-the-art source reconstruction methods and their interrelations.

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“…The goal is to consider acoustic problems in the low frequency range. In numerical 2D and 3D setups it can be shown that the method improves sound source localization at low frequencies [16,17]. Additionally, in [18], the Green's functions from the FEM have been used directly to calculate the steering vectors for numerical beamforming.…”

Section: Introductionmentioning

confidence: 99%

Beamforming for measurements under disturbed propagation conditions using numerically calculated Green's functions

Lehmann¹,

Ernst²,

Schneider³

et al. 2020

Preprint

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Beamforming methods for sound source localization are usually based on free-field Green's functions to model the sound propagation between source and microphone. This assumption is known to be incorrect for many industrial applications and the beamforming results can suffer from this inconsistency regarding both, accuracy of source power estimation, and accuracy of source localisation. The aim of this paper is to investigate whether the use of numerically calculated Green's functions can improve the results of beamforming measurements.The current test cases of numerical and experimental investigations consists of sources placed in a short rectangular duct. The measurement is performed outside the duct in a semi-anechoic chamber. A typical example for this kind of installation is a fan with a heat exchanger.The Green's functions for this test case are calculated numerically using the boundary element method. These tailored Green's functions are used to calculate the corresponding beamforming steering vectors. The weighting of the Green's functions in the steering vectors has a decisive influence on the beamforming results. A generalization of the common steering vector formulations is given based on two scalars. It is shown that arbitrary differentiable Green's functions can be used to find the correct source position or source power level by using the appropriate steering vector formulations.Beamforming measurements are performed using a loudspeaker as a reference source at different positions in the heat exchanger duct. The measurements are evaluated in the frequency domain and by means of different validation criteria it can be shown that the results with the numerical calculated Green's function are improved compared to free field beamforming especially at low frequencies.

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Capabilities of inverse scheme for acoustic source localization at low frequencies

Cited by 7 publications

References 55 publications

An Affordable Acoustic Measurement Campaign for Early Prototyping Applied to Electric Ducted Fan Units

An Affordable Acoustic Measurement Campaign for Early Prototyping Applied to Electric Ducted Fan Units

Uniqueness of an inverse source problem in experimental aeroacoustics

Beamforming for measurements under disturbed propagation conditions using numerically calculated Green's functions

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