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Optimizing noise control treatments in the early design phase is crucial to meet new strict regulations for exterior vehicle noise. Contribution analysis of the different sources to the exterior acoustic performance plays an important role in prioritizing design changes. A method to predict Pass-by noise performance of a car, based on source-path-receiver approach, combining data coming from simulation and experimental campaigns, is presented along with its validation. With this method the effect of trim and sound package on exterior noise can be predicted and optimized.

This article presents a comparative analysis of the influence of different types of flows over fan noise propagation and scattering within the nacelle intake of aircraft turbofan engines. The methodology for the noise simulation is explained. First, the fan noise source is modeled using a boundary condition that represents all the uncorrelated cut-on modes in the interior of the nacelle duct. Then different types of flows and flight conditions are considered in order to determine the influence of the aerodynamic phenomenon in the noise emitted by the nacelle intake. The liner attenuation is also simulated by mean of Myers boundary condition. Finally the results for far field noise are validated against numerical data obtained from the literature for hard and lined wall conditions.

Transmission loss (TL) is a common metric for the comparison of the acoustic performance of mufflers. Muffler TL can be computed from a Boundary Element Method (BEM) model. Perforated tube elements are commonly used in automotive muffler applications. These can be modeled with a detailed BEM model that includes each individual hole in the perforated tube. The main drawback with such a straightforward BEM approach is that the discretionary of the perforated surfaces can result in computationally expensive models. The current work uses an approach that is a more computationally-efficient, yet, precise way of modeling complex mufflers that contain perforated surfaces with BEM. In this approach, instead of explicitly modeling the perforations explicitly they are taken into account as equivalent transfer impedances. There are several models in the literature that can be used to develop the transfer impedance model of the perforated surface.