Experiment and estimation of the sound absorption coefficient for clearance of corrugated honeycomb

The sound absorption coefficient of thin tubes with a honeycomb-corrugated structure was estimated via theoretical analysis assuming the dimensions of the tube and the known physical properties of air. This analysis yields a propagation constant and characteristic impedance, which can be modeled as a one-dimensional transfer matrix. The sound absorption coefficient is then calculated by the transfer-matrix method and the results of comparison with the experiments are reported. The corrugated clearance was divided into elements for which approximations that assumed the clearance between two planes and took into account the perimeter and cross-sectional area of each element were considered. The theoretical value of the sound absorption coefficient obtained using this method was shown to be in good agreement with the experimental results. The experimental value of the sound absorption coefficient was larger than the theoretical value in the previous method in the analysis wherein each divided element was approximated by the distance between two planes taking into account the thickness and cross-sectional area of the clearance.