Publications on the topics of propeller source noise, airborne noise transmission, and passenger comfort response to noise and vibration are reviewed. Of the 187 publications referenced, 140 have appeared since 1978. Examples of research accomplishments are presented to illustrate the state of the art. Emphasis is on comparisons of theoretical and measured results, but the description of the theories is left to the references. This review shows that substantial progress has been made in understanding the characteristics of propeller noise, airborne noise, and passenger response, and in the development of prediction methods. Application of the technology to cabin noise control and possible future research directions are discussed.

Review of recent research on interior noise of propeller aircraft

Review of recent research of interior noise of propeller aircraft

In order to understand the effects of installation on propeller noise, numerous measurements are required to define the directivity of the noise as well as the level. An experimental study was designed to map the noise radiation pattern for various single-rotation propeller (SRP) installations and one counter-rotation propeller (CRP) installation covering an area ± 60 deg from the propeller disk plane and ± 60 deg laterally. The configurations considered included an SRP at angle of attack and in tractor and pusher operations and a CRP. A firstprinciples linear theory was validated for the SRP tractor operation over the angle range mentioned above. The increases in noise that arise from an unsteady loading operation such as an SRP pusher or a CRP exceed 15 dB and depend on the observer location. In particular, the majority of the additional noise from the unsteady loading appears to radiate in the axial directions.

Noise radiation patterns of counter-rotation and unsteadily loaded single-rotation propellers

An analytical model was developed to predict the interior noise of propeller-driven aircraft The fuselage model is that of a cylinder with a structurally-integral floor The cabin sidewall is stiffened by stringers and ring frames, and the floor by longitudinal beams The cabin interior is covered with a sidewall treatments consisting of layers of porous material and an impervious trim septum Representation of the propeller pressure field is utilized as input data in the form of the propeller noise signature at a series of locations on a grid over the fuselage structure Results obtained from the analytical model are compared with test data measured by NASA in a scale model cylindrical fuselage excited by a model propeller

https://ntrs.nasa.gov/api/citations/19840021618/downloads/19840021618.pdf

Propeller aircraft interior noise model

Advanced turboprop blade designs and new propeller installation schemes motivated an effort to include unsteady loading effects in existing propeller noise prediction computer programs. The present work validates the prediction capability while studing the effects of shaft inclination on the radiated sound field. Classical methods of propeller performance analysis supply the time-dependent blade loading needed to calculate noise. Polar plots of the sound pressure level (SPL) of the first four harmonics and overall SPL are indicative of the change in directivity pattern as a function of propeller angle of attack. Noise predictions are compared with newly available wind tunnel data and the accuracy and applicability of the prediction method are discussed. It is concluded that unsteady blade loading caused by inclining the propeller with respect to the flow changes the directionality and the intensity of the radiated noise. These changes are well modeled by the present quasi-steady prediction method.

Predicted Changes in Advanced Turboprop Noise with Shaft Angle of Attack

Classical methods of propeller performance analysis are coupled with state-of-the-art Aircraft Noise Prediction Program (ANOPP:) techniques to yield a versatile design tool, the NASA Generalized Advanced Propeller Analysis System (GAPAS) for the novel quiet and efficient propellers. ANOPP is a collection of modular specialized programs. GAPAS as a whole addresses blade geometry and aerodynamics, rotor performance and loading, and subsonic propeller noise.

S. L. Padula

Papers

Acoustic prediction methods for the NASA generalized advanced propeller analysis system (GAPAS)