An Experimental Study of Propeller - Induced Structural Vibration and Interior Noise

This paper presents results of tests conducted to study fuselage sidewall dynamics and their effects on the cabin interior noise of a twin-engine, propeller-driven, light aircraft. Data on the dynamic behavior were obtained by slowly sweeping the RPM of one of the engines while the aircraft was stationary on the ground. This technique allowed frequency response plots of the sidewall structural accelerations to be obtained. These accelerations are compared to similar results from a test using a mechanical shaker in order to evaluate the structural dynamic response caused by the harmonics of the propeller blade passage tone. The dynamic response of the fuselage sidewall is also discussed as a noise transmission mechanism. A second mechanism for noise transmission through the fuselage sidewall was investigated by opening the copilot's window. The results illustrate the complex nature of the noise transmission mechanisms and the importance of correctly assessing noise paths.