On Sound Transmission into a Thin Cylindrical Shell under "Flight Conditions"
In the context of the transmission of airborne noise into an aircraft fuselage, a mathematical model for sound transmission into a thin cylindrical shell is used to study sound transmission under -œflight conditions-: i.e., under conditions of external air flow past a pressurized cylinder at flight altitude. Numerical results for different incidence angles are presented for a typical narrow-bodied jet in cruising flight at 10 660 m (35 000 ft) with interior pressure at 2440 m (8000 ft). A comparison is made between no-flow sound transmission at standard conditions on the ground to sound transmission under flight conditions. It is shown that at M = 0, the cylinder transmission loss has dips at fR (cylinder ring frequency) and fc (critical frequency for a flat panel of same material and thickness as shell). Below fR cylinder resonances affect TL. Between fR and fc, cylinder TL follows a masslaw behavior. Flow provides a modest increase in TL in the mass-law region, and strongly interacts with the cylinder resonances below fR. For normally-incident waves, TL is unaffected by flow.
L. R. Koval, "On Sound Transmission into a Thin Cylindrical Shell under "Flight Conditions"," Journal of Sound and Vibration, Elsevier, Jan 1976.
The definitive version is available at http://dx.doi.org/10.1016/0022-460X(76)90465-X
Mechanical and Aerospace Engineering
Article - Journal
© 1976 Elsevier, All rights reserved.