When wakes from the fan strike downstream stator vanes annoying tone noise can result.

V072:
Predicated on simplistic models of the flow and fan geometry, V072 has been proven useful in studying rotor/stator interaction noise. When you need to design a quiet fan stage, tone noise trends from V072 can help you make smart choices for important parameters like blade/vane count, rotor/stator spacing, and stator orientation. When you’re after quick noise estimates early in the design cycle, V072 may be your tool of choice.

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TFaNS:
Taking rotor/stator interaction noise prediction to the next level, not only can TFaNS calculate the tone noise created by the rotor or stator individually, it can also account for the blade row coupling effects such as transmission and reflection and can propagate those tones to the far field. Like V072, TFaNS runs quickly since it models the blades and vanes as 2-D cascades of twisted flat plates, and employs semi-empirical fan wake models.

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Linflux:
When simple models are too simple, an analysis with Linflux gives you the power to study realistic, 3-D flows and blade geometries. Linflux is more computationally intensive since it uses flow solutions from a Computational Fluid Dynamics (CFD) code as input. Like all the software developed by the NASA Glenn Acoustics Branch, Linflux has been rigorously validated against experimental data. 

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MPT:
Multiple pure tone noise (aka “buzz saw” noise), created by rotor locked shocks present when the fan blade tip speed is supersonic, can be estimated with the MPT code.  The MPT codes also use flow predictions from a Computational Fluid Dynamics (CFD) code as input.  This tool can be used by engineers to study the real-world effects of blade-to-blade difference caused during fabrication (manufacturing variations) or during hot-running operation (blade setting angle and untwist variations).

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   page for more info on the MPT codes

WOBBLE:
Propeller noise can be strongly affected by any inflow that leads to unsteady blade loading. The WOBBLE code computes the tone noise associated with propellers with varying inflow angle and predicts the axial and circumferential directivity. Inflow angle is specified in terms of yaw, pitch, and roll angles of the aircraft. The acoustic model is exact and accounts for all unsteady sources such as thickness and loading effects from the blades.

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   page for more info on the WOBBLE code

BASS: (In Development)
The BASS code is a high-accuracy parallel computational aeroacoustics code which solves the Euler and Navier-Stokes equations to directly predict unsteady flow, noise generation, and noise propagation. The BASS code has been validated for three-dimensional wake-stator tone noise prediction. Currently, the BASS code is being extended to predict turbulent broadband wake-stator noise, using experimental data to prescribe the unsteady rotor wakes. The BASS code is general-purpose and has been applied to a range of aeroacoustic cases.