A theoretical and experimental investigation of the effects of the interaction between an acoustic field and cylindrical structure on sound transmission loss

A theoretical and experimental investigation of the transmission of sound through the walls of a hollow cylinder is pursued by analyzing the interaction between the sound field and structural vibrations. The method used to investigate the problem is based on an energy balance between the internal acoustic field and the vibrational field of the cylinder wall. After the energy balance is established to determine the parameters to be analyzed, each parameter is then examined separately to determine its effect on the overall solution. Statistical energy methods are used to reduce the complexity of the analysis caused by the high number of interacting modes. Initial tests were conducted with a stationary acoustic field in an air filled cylinder and the static pressure near zero. These showed good agreement with the theory in pipes ranging in diameter from 4 to 12 inches and with wall thickness from .237 to .531 inches. When the static pressure was increased, this resulted in an increase in the density of the fluid. The change in transmission loss due to the static pressure increase was correctly predicted by the current analysis.