@ARTICLE{Meissner_Mirosław_Effect_2010, author={Meissner, Mirosław}, volume={vol. 35}, number={No 3}, journal={Archives of Acoustics}, pages={421-435}, howpublished={online}, year={2010}, publisher={Polish Academy of Sciences, Institute of Fundamental Technological Research, Committee on Acoustics}, abstract={A simple analytical method is developed to estimate frequencies of longitudinal modes in closed hard-walled ducts with discontinuities in a cross-sectional area. The approach adopted is based on a general expression for the acoustic impedance for a plane wave motion in a duct and conditions of impedance continuity at duct discontinuities. Formulae for mode frequencies in a form of transcendental equations were found for one, two and three discontinuities in a duct cross-section. An accuracy of the method was checked by a comparison of analytic predictions with calculation data obtained by use of numerical implementation based on the forced oscillator method with a finite difference algorithm.}, type={Artykuły / Articles}, title={Effect of Cross-Sectional Area Discontinuities in Closed Hard-Walled Ducts on Frequency of Longitudinal Modes}, URL={http://www.czasopisma.pan.pl/Content/107547/PDF/91.pdf}, doi={10.2478/v10168-010-0034-0}, keywords={longitudinal duct modes, discontinuity in duct cross-section, contraction ratio}, }