Over the last few decades, noise related concerns have played a major role in the development of aircraft engines. The previously dominant jet noise mechanisms are now being replaced by tonal and broadband noise from the fan and interactions from the fan wakes and the downstream stator. Alternately, engine inlet and exhaust ducts are being fitted with sophisticated liner materials that aid in damping fan related noise. In this paper, the authors investigate the radiation problem from the engine inlets with the aid of numerical simulations of the Euler/Navier-Stokes equations coupled with a time-domain methodology that analyzes the impedance characteristics of liner materials. In doing so, the authors present a simulation capability that can be used to identify and analyze tonal noise from high bypass ratio engines with acoustically treated nacelles. In this paper, we carry out numerical experiments and present results of radiation from two different engine inlet geometries with lined ducts. © 2001 by the authors.