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Designing modern turbofan engines with higher bypass ratios is significantly limited by increasingly restrictive airport noise regulations. Independent of takeoff, cruise or landing operations, the fan rotor-stator interactions remain as one of the major engine sources of noise. Therefore, interest in understanding, modeling and eventually redudng this noise has increased the need for advanced Computational Aero%Acousflcs (CAA) codes to serve as a primary tool in the fan design process. Two years ago, Pratt & Whitney Canada (PWC) initiated a research effort to develop a fan tone generation and radiation system. As displayed in figure 1, this system integrates three in-house computational tools: a CFD fan analysis code such as NS3D, a CAA linear and nonlinear radiation codes, and a fan tone generation module which serves as a link between these CFD and CAA codes. NS3D is a PWC proprietary code which solves the 3D Navier-Stokes equations for turbomachinery and external flow problems by using an SUPG finite element method on structured and unstructured grids. The development and the validation of this code was already dealt with in reference 1 and here, will be mainly used to perform 3D unsteady rotor-stator analyses of fan stages. Therefore, the present paper focuses on the development of a noise generation module which computes the incident fan tone modes, as well as on the validation of the PWC CAA codes that serve in the propagation of th%noise sources to the far-field. Both axisymmetric, nonlinear and linear CAA codes 2,3 were developed for noise radiation from aircraft engines and, more specifically, for fan tone radiation computations. The nonlinear in-house codes, based on the Euler equations with a multidomain spectral method in space and an explicit 2N-storage Runge-Kutta in time, were first developed to achieve a more complete modelling of sound propagation phenomena., The original document contains color images. Presented at the RTO Applied Vehicle Technology Panel (AVT) Symposium, 8-11 Oct 2001, Manchester, United Kingdom, p(SYA)6-1/(SYA)6-12. This article is from ADA415749 Aging Mechanisms and Control. Symposium Part A - Developments in Computational Aero- and Hydro-Acoustics. Symposium Part B - Monitoring and Management of Gas Turbine Fleets for Extended Life and Reduced Costs (Les mecanismes vieillissants et le controle) (Symposium Partie A - Developpements dans le domaine de l'aeroacoustique et I'hydroacoustique numeriques) (Symposium Partie B - Le sui