Tonal-Noise Assessment of Quadrotor-Type UAV Using Source-Mode Expansions

Roger, Michel; Moreau, Stéphane

doi:10.3390/acoustics2030036

Cited by 32 publications

(8 citation statements)

References 23 publications

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“…As pointed out in ref. 12, steady-loading noise is significant, even at relatively low Mach numbers characteristic of drone rotors, for low blade numbers and BPF harmonic orders. However, the envelope of the tonal-noise spectrum is expected to decrease fast and quite regularly, which is obviously not the case in the present free-field measurements.…”

Section: Analysis Of Resultsmentioning

confidence: 99%

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Acoustic versus aerodynamic installation effects on a generic propeller-driven flying architecture

Roger

Giraldo

Jacob

2022

International Journal of Aeroacoustics

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The present work addresses the combined aerodynamic and acoustic installation effects observed as a subsonic propeller is partly crossing the near-wake of a wing. Only the tonal noise at multiples of the blade passing frequency is considered. The aerodynamic effect is the onset of additional sound sources caused by blade-wake interaction, compared to the case of the isolated propeller. The acoustic effect is the scattering by the wing. The work is aimed at demonstrating the ability of analytical models to estimate separately these effects, which is of primary interest for the preliminary design steps of a system. A basic experiment carried out in an anechoic, open-jet facility, is described, for validation purposes. The far-field sound measurements are compared to the predictions and some key outcomes are presented. In particular, the model provides guidelines to avoid configurations of excessive noise.

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Section: Analysis Of Resultsmentioning

confidence: 99%

“…The expression is valid everywhere in space, as discussed, for instance, in refs. 11, 12. It holds for a pure axial-flow architecture, both terms in the brackets corresponding to the axial and tangential components of the blade force, respectively.…”

Section: Free-field Sound Radiation Formulationsmentioning

confidence: 98%

Acoustic versus aerodynamic installation effects on a generic propeller-driven flying architecture

Roger

Giraldo

Jacob

2022

International Journal of Aeroacoustics

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“…It will inspire new measurement and post-processing procedures to support noise regulations and the assessment of the noise impact on communities [37,38]. For instance, this can be achieved by including BPFM aspects in realistic auralizations of rotorcraft noise [20,39] and future noise prediction tools [21,[40][41][42].…”

Section: B Present Contribution and Outlinementioning

confidence: 99%

Low-Frequency Intensity Modulation of High-Frequency Rotor Noise

Baars

Ragni

2023

AIAA AVIATION 2023 Forum

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Acoustic spectra of rotor noise yield frequency-distributions of energy within pressure time series. However, they are unable to reveal phase-relations between different frequency components, while the latter play a role in low-frequency intensity modulation of higherfrequency rotor noise. Baars et al. (AIAA Paper 2021-0713) outlined a methodology to quantify inter-frequency modulation, which in the current work is applied to a comprehensive acoustic dataset of a rotor operating at low Reynolds number at advance ratios ranging from 𝐽 = 0 to 0.61. The findings strengthen earlier observations for the case of a hovering rotor, in which the modulation of the high-frequency noise is strongest at angles of 𝜃 ≈ −20 • (below the rotor plane). For the non-zero advance ratios, modulation becomes dominant in the sector −45 • ≲ 𝜃 ≲ 0 • , and is maximum in strength for the highest advance ratio tested (𝐽 = 0.61). Intensity-modulation of high-frequency noise is primarily the consequence of a far-field observer experiencing a cyclic sweep through the noise directivity patterns of the relatively directive trailing-edge/shedding noise component. This noise becomes more intense with increasing J and is associated with the broadband features of the (partially) separated flow over the rotor blades.

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“…36 Finally, BPF modulation aspects are critical for achieving realistic auralizations of rotorcraft noise, 37 and likewise, BPF modulation characteristics will benefit future extensions of noise prediction tools. [38][39][40][41]…”

Section: B Present Contribution and Outlinementioning

confidence: 99%

Quantifying modulation in the acoustic field of a small-scale rotor using bispectral analysis

Baars

Bullard

Mohamed

2021

AIAA Scitech 2021 Forum

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This paper describes a methodology to quantify inter-frequency modulation in the acoustic field of a small-scale rotor. How the blade passing frequency modulates the intensity of the higher-frequency (broadband) noise content is of specific interest, as this modulation is a major factor in the human perception of rotor noise from advanced air mobility vehicles and drones. A proposed modulation-parameter is based on post-processing steps that are applicable to a single acoustic time series. First, an auto-bispectral analysis assesses the dominant nonlinear, quadratic inter-frequency coupling between the blade passing frequency and the higher-frequency noise content. Secondly, the degree of modulation is determined using a robust parameter: a correlation parameter between the (low-frequency) modulating BPF signal and an envelope of the (higher-frequency) carrier signal. Provided that a single parameter is obtained for a given acoustic time series, the directivity pattern of the modulation strength can be inferred from data available from standard acoustic measurement campaigns. For illustration, an 11 inch diameter single-rotor in hover is considered, with acoustic data taken at 420 microphone positions within a plane perpendicular to the rotor disk. It is revealed that modulation is confined to a sector θ ≈ (10 • , −45 • ), where θ = 0 • is the rotor plane and negative angles are in the direction of the rotor-induced flow. The strongest modulation appears around θ ≈ −15 • . This work aids in quantifying the phenomenological description of modulation, namely that it results from the periodic advance and retreat of certain rotor blade's noise sources, relative to a stationary observer.

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Tonal-Noise Assessment of Quadrotor-Type UAV Using Source-Mode Expansions

Cited by 32 publications

References 23 publications

Acoustic versus aerodynamic installation effects on a generic propeller-driven flying architecture

Acoustic versus aerodynamic installation effects on a generic propeller-driven flying architecture

Low-Frequency Intensity Modulation of High-Frequency Rotor Noise

Quantifying modulation in the acoustic field of a small-scale rotor using bispectral analysis

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