Effect of Air Flow, Panel Curvature, and Internal Pressurization on Field-Incidence Transmission Loss
In the context of sound transmission through aircraft fuselage panels,equations for the field-incidence transmission loss (TL) of a single-walled panel are derived that include the effects of external air flow, panel curvature, and internal fuselage pressurization. These effects are incorporated into the classical equations for the TL of single panels, and the resulting double integral for field-incidence TL is numerically evaluated for a specific set of parameters. Flow is shown to provide a modest increase in TL that is uniform with frequency up to the critical frequency. The increase is about 2 dB at Mach numberM = 0.5, and about 3.5 dB at M = l. Above the critical frequency where TL is damping controlled, the increase can be slightly larger at certain frequencies. Curvature is found to stiffen the panel, thereby increasing the TL at low frequencies, but also to introduce a dip (analogous to the coincidence dip at the critical frequency) at the --ring frequency-- of a full cylinder having the same radius as the panel. This effect, up to now qualitatively understood, can now be quantitatively estimated. Pressurization appears to produce a slight decrease in TL throughout the frequency range, and also slightly shifts the dips at the critical frequency and at the ring frequency.
L. R. Koval, "Effect of Air Flow, Panel Curvature, and Internal Pressurization on Field-Incidence Transmission Loss," Journal of the Acoustical Society of America, Acoustical Society of America (ASA), Jan 1976.
The definitive version is available at https://doi.org/10.1121/1.381024
Mechanical and Aerospace Engineering
Keywords and Phrases
Acoustical Effects; Integral Equations; Acoustic Transmission; Aircraft; Mach Numbers; Panel Damping
Article - Journal
© 1976 Acoustical Society of America (ASA), All rights reserved.