Investigations into Vibration and Sound Transmission Characteristics of Cylindrical Shells

Abstract

This thesis describes an analytical and experimental study of the relationship between cylinder wall vibration and the resultant acoustic energy generated inside an enclosed stiffened cylinder representative of an aircraft fuselage. The work included measuring vibration and noise transmission properties of models simulating a fuselage. The results from these tests were used in the analytical predictions. Experimental facilities were developed for this work to measure parameters such as space average vibration and sound pressure levels, structural damping, transmission loss together with other relative parameters. Three cylindrical shell configurations were tested. Extensive experimental measurements were carried out to study various effects which are reported on noise and vibration characteristics. An emphirical approach was taken, to account for the internal loss factor. With this approach, a significant improvement was obtained in the comparison between analysis and experiment. relationship between the cylinder wall vibration and noise transmission characteristics were measured for both acoustical and mechanical forms of excitation. Below the ring frequency there was no direct comparison between the two measurements. Computer programs were. developed for the theoretical study of natural frequencies of cylinders and plates, and results are presented in the form of graphs and tables.