AN EXPERIMENTAL-STUDY OF THE ACOUSTIC CHARACTERISTICS OF PERFORATED PIPE IN TERMS OF WAVE-NUMBER AND POROSITY

Abstract

The acoustic characteristics of perforated pipes have been experimentally studied in terms of transmission loss. This study includes perforated pipes having both uniform and non-uniform hole distributions along the length. The major experimental parameters are the global porosity, which is defined as the ratio of the total area of the holes in the wail of the pipe to the pipe's cross-sectional area, and the non-dimensional wavenumber ka; k is the propagation constant and a is the distance between the perforated holes in the axial direction of the pipe. The experimental results provide information about the acoustic characteristics of perforated pipes for both the low and the high wavenumber regions. It is found that for high wave numbers that a non-uniform distribution of the holes affects only the transmission loss, and the number of holes distributed along the pipe affects the acoustic impedances of the individual holes and greatly influences the transmission loss.