Methods for the prediction of airframe aerodynamic noise

Revell, J. D.; Healy, G. J.; Gibson, John S.

doi:10.2514/6.1975-539

Cited by 10 publications

(3 citation statements)

References 9 publications

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“…(1), we see that the far field acoustic pressure is (4) for X = /x = 90 deg, and from Eq. (3) we see that the average aerodynamic lifting pressure on the wing surface is Pae=H ence, the ratio of the two quantities is…”

Section: Physical Interpretation Of the Noise Coefficientsmentioning

confidence: 93%

“…where the acoustic range angle X and the sideline angle /x are both 90 deg; that is, where the ground-based microphone is directly below the flight path, where C, is the dimensionless Presented as Paper 77-1272 at the AIAA 4th Aero-Acoustics Conference, Atlanta, Ga., Oct. [3][4][5]1977 coefficient, where SPL C is the sound pressure level corrected for the effects of atmosphere absorption and turbulence, and where the dimensional factors are lumped in the parameter (2) where R is the acoustic radius, M is the flight Mach number, P 0 is the acoustic reference pressure (20 x 10 ~6 Pa) p a is the atmospheric pressure, and S w is the reference or wing area.…”

Section: Nondimensionalization Of Airframe Noisementioning

confidence: 99%

“…Hardin et al, 2 Munson, 3 Revell et al, 4 and Bauer and Munson. 5 A current problem is the difficulty in correlating all the results, inasmuch as sound levels are generally presented in decibels, which are related to a dimensional quantity; that is, although decibels are dimerisionless, a decibel measurement of noise represents a definite sound pressure, which has the dimensions of force divided by area.…”

Section: Introductionmentioning

confidence: 97%

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Dipole Modeling and Nondimensionalization of Airframe Noise

Bauer¹

1979

Journal of Aircraft

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Airframe noise measurements may be correlated and made more physically meaningful by a conversion from a decibel or dimensional form to a coefficient or nondimensional form, in particular for radiation in a single direction, chosen to be directly below the aircraft. For radiation in other directions, a three-dipole model may be used, and three additional coefficients defined. Examples of the coefficients are given for various flight and configuration conditions for both the DC-9-31 and the DC-10-10 aircraft. A significant body of airframe noise data has been published and is available for conversion to nondimensional form, both for the representation of overall sound pressure levels and for any one or more one-third octave band levels.

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Section: Physical Interpretation Of the Noise Coefficientsmentioning

confidence: 93%

Section: Nondimensionalization Of Airframe Noisementioning

confidence: 99%

Section: Introductionmentioning

confidence: 97%

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Dipole Modeling and Nondimensionalization of Airframe Noise

Bauer¹

1979

Journal of Aircraft

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Airframe aerodynamic noise—total radiated acoustic power approach

Shaw

Houser

1978

The Journal of the Acoustical Society of America

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During flight the noise radiated by aircraft is emanating from two distinct types of sources. One source is the propulsion system and the other is the nonpropulsion system noise, or airframe noise, associated with movement of the aircraft through the atmosphere. The purpose of this effort was to study airframe noise using a total radiated acoustic power approach. Methodology was developed to accurately calculate the total acoustic power by using measurements from an array of microphones during aircraft flyover. This methodology was applied to Schweizer 2–32 glider flyovers and it was found that for an aerodynamic configuration (no flaps, wheels, wheel wells, etc.) the total acoustic power can be obtained from one flyover measurement by assuming the directivity is nearly equal in all directions. This assumption was shown to be valid for the glider and is assumed valid for any aircraft in an aerodynamic configuration. The detailed methodology developed is still useful since most commercial aircraft land in a nonaerodynamic configuration and thus their directivity is not equal in all directions. The results from the glider tests were compared to data in the literature and found to agree well. Variation of the total power with aircraft velocity followed a V6 law. The parameter which best normalizes the overall acoustic power from different aircraft was found to be the wing area.

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Assessment of airframe noise

Block

1979

Journal of Aircraft

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A component method of airframe noise prediction is used to predict levels of operational and proposed aircraft airframe noise to assess the contribution of airframe noise to community noise levels. This is done after first evaluating the prediction method using newly acquired detailed measurements from full-scale aircraft and models. In the course of the evaluation, modeling techniques of airframe noise sources are examined with attention to scaling. Finally, when used to predict approach airframe EPNL's, the levels fell about 10 EPNdB below current noise regulations and about 5 EPNdB below proposed noise regulations. Nomenclature b w = wing span C If C 2 = empirical constants in Eq. (2) c = ambient speed of sound / = frequency f m = frequency of maximum predicted SPL h = airplane altitude N = parameter used in Eq. (1) J} 2 = mean-square acoustic pressure S w = wing area V -airspeed 5 f -trailing-edge flap deflection 5 W = boundary-layer thickness at the trailing edge of the wing 0 = flyover angle = sideline angle v -kinematic viscosity

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Methods for the prediction of airframe aerodynamic noise

Cited by 10 publications

References 9 publications

Dipole Modeling and Nondimensionalization of Airframe Noise

Dipole Modeling and Nondimensionalization of Airframe Noise

Airframe aerodynamic noise—total radiated acoustic power approach

Assessment of airframe noise

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