Separation of Main and Tail Rotor Noise from Ground-Based Acoustic Measurements

Greenwood, Eric; Schmitz, Fredric H.

doi:10.2514/1.c032046

Cited by 12 publications

(9 citation statements)

References 5 publications

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“…The analytical models resulting from the parameter identification method were able to estimate BVI noise levels in directions th at were difficult to capture using the authors' previous rotor harmonic noise measurement technique [6]. The method also facilitated the accurate estimation of BVI noise at flight conditions not included in the set of measured data, even across wide variations in the non-dimensional governing parameters where standard "data-driven" interpolation of the measured noise levels failed.…”

Section: Discussionmentioning

confidence: 90%

“…[6] However, the theory was limited by the assumption that all noise from the rotor radiated from a single point on the rotor hub. In reality, the actual rotor noise sources are distributed on or near the plane of the rotor.…”

Section: Nomenclaturementioning

confidence: 99%

“…Tip vortices roll-up somewhat inboard of the blade tips, and the diameter of the wake will proceed to contract over time. The parametric variations of these effects are included in the model by including two additional dependent modeling parameters : (6) where r r is the dependent parameter controlling initial tip vortex roll-up radius, D is the dependent parameter controlling the rate of wake contractio n, and 1 = 0.145 + 27CT , as suggested by Landgrebe. [14] In addition to the wake geometry, there are other mechanisms that control the strength of BVI noise and are governed by the non-dimensional parameters.…”

Section: Technical Approachmentioning

confidence: 99%

“…A time domain deDopplerization technique [6] is applied to transform ground based noise measurements to those that would be measured by a set of "virtual inflight observers" traveling with the helicopter through the medium with approximately fixed measurement geometry -this is analogous to the noise measurement of a rotor in a wind tunnel.…”

Section: Technical Approachmentioning

confidence: 99%

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A Parameter Identification Method for Helicopter Noise Source Identification and Physics-Based Semiempirical Modeling

Greenwood¹,

Schmitz

2018

j am helicopter soc

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A new physics-based parameter identifi cation method for rotor harmonic noise sources is developed using an acoustic inverse simulation technique. This new method allows for the identification of individual rotor harmonic noise sources and allows them to be characterized in terms of their individual non-dimensional governing parameters. This new method is applied to both wind tunnel measurements and ground noise measurements of two-bladed rotors. The method is shown to match the parametric trends of main rotor Blade-Vortex Interaction (BVI) noise, allowing accurate estimates of BVI noise to be made for operating conditions based on a small number of measurements taken at different operating conditions. Nomenclature

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Section: Discussionmentioning

confidence: 90%

Section: Nomenclaturementioning

confidence: 99%

Section: Technical Approachmentioning

confidence: 99%

Section: Technical Approachmentioning

confidence: 99%

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A Parameter Identification Method for Helicopter Noise Source Identification and Physics-Based Semiempirical Modeling

Greenwood¹,

Schmitz

2018

j am helicopter soc

Self Cite

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“…6 This was made possible by using a source noise definition that generated separate main and tail rotor pressure time histories for a single blade passage. 7 For each rotor, unsteadiness of the source was removed by applying synchronous time averaging of multiple blade passages. The propagation model used was also absent of turbulence.…”

Section: Introductionmentioning

confidence: 99%

A Recording-Based Method for Auralization of Rotorcraft Flyover Noise

Pera

Rizzi

Krishnamurthy

et al. 2018

2018 AIAA Aerospace Sciences Meeting

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Rotorcraft noise is an active field of study as the sound produced by these vehicles is often found to be annoying. A means to auralize rotorcraft flyover noise is sought to help understand the factors leading to annoyance. Previous work by the authors focused on auralization of rotorcraft fly-in noise, in which a simplification was made that enabled the source noise synthesis to be based on a single emission angle. Here, the goal is to auralize a complete flyover event, so the source noise synthesis must be capable of traversing a range of emission angles. The synthesis uses a source noise definition process that yields periodic and aperiodic (modulation) components at a set of discrete emission angles. In this work, only the periodic components are used for the source noise synthesis for the flyover; the inclusion of modulation components is the subject of ongoing research. Propagation of the synthesized source noise to a ground observer is performed using the NASA Auralization Framework. The method is demonstrated using ground recordings from a flight test of the AS350 helicopter for the source noise definition.

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Auralization of air vehicle noise for community noise assessment

Rizzi

Sahai

2019

CEAS Aeronaut J

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Separation of Main and Tail Rotor Noise from Ground-Based Acoustic Measurements

Cited by 12 publications

References 5 publications

A Parameter Identification Method for Helicopter Noise Source Identification and Physics-Based Semiempirical Modeling

A Parameter Identification Method for Helicopter Noise Source Identification and Physics-Based Semiempirical Modeling

A Recording-Based Method for Auralization of Rotorcraft Flyover Noise

Auralization of air vehicle noise for community noise assessment

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