Effects of Cavity Diameter on Acoustic Impedance in a Complex Acoustic Environment

Brown, M C ; Jones, M G

关键词: ACOUSTICS;    ACOUSTIC IMPEDANCE;    ACOUSTIC PROPERTIES;    AIRCRAFT NOISE;    CAVITIES;    DIAMETERS;    LININGS;    SUBSONIC SPEED;   

RP-ID  :  NF1676L-28604

学科分类：航空航天科学

美国|英语

来源: NASA Technical Reports Server

【 摘 要 】

This paper investigates the effects of cavity diameter on the acoustic performance of conventional perforate-over-honeycomb liners. This investigation is a follow up to a previous study where it was demonstrated that the cavity diameter has a relatively small effect on the acoustic impedance for core cavity diameters up to 2.0 inches. In the current study, liner concepts are exposed to a complex acoustic environment, where higher-order modes are present. Four liner configurations are explored in this investigation, which include two cavity cores of different cavity diameters combined with two facesheets. These configurations are tested in the Grazing Flow Impedance Tube (GFIT) at Mach 0.0, 0.3, and 0.5 at a source sound pressure level of 150 dB. A comparison of the acoustic performance of these samples suggests that the cavity diameter has a relatively small effect on the acoustic impedance for core cavity diameters up to 2.0 inches at these conditions. These configurations are exposed to a more complex acoustic environment (e.g., higher-order modes) in the Curved Duct Test Rig (CDTR) at Mach 0.0 and 0.3.