Impedance Eduction for Multisegment Liners

Jones, M G ; Watson, W R ; Nark, D M ; Howerton, B M

关键词: ACOUSTIC ATTENUATION;    ACOUSTIC IMPEDANCE;    ADDITIVE MANUFACTURING;    AERODYNAMIC NOISE;    COMMERCIAL AIRCRAFT;    LININGS;    PRESSURE MEASUREMENT;    WALLS;    ALGORITHMS;    BOUNDARY CONDITIONS;    FINITE ELEMENT METHOD;    HONEYCOMB STRUCTURES;    MICROPHONES;    SOUND PRESSURE;   

RP-ID  :  NF1676L-28585

学科分类：声学和超声波

美国|英语

来源: NASA Technical Reports Server

【 摘 要 】

This paper explores the validity of an indirect method for impedance eduction of multisegment liners. This is accomplished via results obtained with two uniform liners and one two-segment liner, where each segment is constructed to match the geometry of one of the uniform liners. Each uniform liner is evaluated using direct and indirect impedance eduction methods. An indirect impedance eduction method is used to educe the impedance for each segment of the two-segment liner, and the results are compared with those educed for the uniform liners. These impedance spectra are shown to compare favorably for the majority of test conditions. Poorer comparisons are achieved for those test conditions where one segment of the two-segment liner provides little attenuation. Poor attenuation is a wellknown cause for impedance eduction difficulties. Overall, this multisegment impedance eduction method offers the potential to study complicated liners in a more efficient manner (i.e., without the requirement to build and test separate liners to duplicate each unique segment of the multisegment liner). More detailed studies are required to further validate this tool, and are intended to be the focus of future research.