Noise Reduction Using Finite-Length Flexible Segments

Abstract

In this work, the reduction of acoustic noise in piping systems through the installation of finite flexible segments is explored. A mathematical model describing the relevant parameters is developed. To verify the model, experimental work is undertaken using rubber hoses as flexible segments and air as the contained fluid. The effect of the segment on propagating acoustical energy is studied in terms of its insertion loss. Both theoretical and experimental results indicate that, for light fluid loading, the flexibility of the segment is only important when significant axial shell resonances exist, or when one or both acoustical termination impedances at the ends of the segment are much larger or smaller than the characteristic impedance of the medium. Further, the model indicates that for heavier fluid loading (i.e., when the compressibility of the flexible section is significant in relation to the bulk compliance of the fluid), in addition to higher associated insertion losses, the finite length resonances become more pronounced, and performance is less sensitive to small variations in the termination impedances. [S0739-3717(00)00402-5]