Theoretical and experimental study of sound propagation in ducts with spatially periodic area changes
Sound propagation of one-dimensional waves through a tube with periodic area changes is studied theoretically and experimentally. The resulting wave behavior is similar to that observed for periodic structures, with Bloch waves, pass-bands and stop-bands. The feasibility of this configuration is studied as a method to reduce sound propagation and radiation from noise sources having harmonics that fall in the stop bands. This approach to noise reduction is shown to give substantial attenuation. The bandwidth of the stop bands makes the design robust so that careful tuning is not required. Performance for broadband sound reduction is also evaluated. The relationship between area change parameters and the location and width of stop-bands is discussed. Experimental measurements show good agreement with theoretical predictions as long as the actual geometry is accurately modeled.
