Abstract

ARENAS, Jorge P; AGUAYO, Juan L; GERGES, Samir N.Y  and  POBRETE, Víctor H. Characterization of the Acoustic Input Impedance for Reactive Expansion Chambers. Inf. tecnol. [online]. 2006, vol.17, n.3, pp.117-122. ISSN 0718-0764.  http://dx.doi.org/10.4067/S0718-07642006000300017.

This article compares the results of two theoretical models for characterizing the input impedance of reactive expansion chambers. One method consists of a numerical integration of a non-linear differential equation for the plane wave sound propagation through ducts of varying cross-sections. The second is the classical transfer matrix method. The estimated values are compared with experimental results obtained for four geometrical cases, measured by means of the two-microphone technique and the transfer function. The results show that the estimates using the numerical method give values comparable in accuracy to the transfer matrix method. Introduction of a complex wave number allows quantification of the attenuation of the sound waves inside the ducts. Thus, the numerical method allows application of the method in cases where the transfer matrices are not defined.

Keywords : expansion chambers; acoustic impedance; transfer matrix; noise control; mufflers.