Improvement of acoustic models for community noise exposure prediction

This paper presents a method to predict environmental noise produced by military aircraft with twin engine and non-axisymmetric jets. The method builds on the SAE Aerospace Recommended Practice for predicting the noise of a single exhaust jet. A first assessment of the reliability of the prediction is made, with comparison with published data. Earlier studies on twin jets are then used to model the variation in sound pressure level frequency spectra with polar and azimuthal angles as well as a function of jet temperature and velocity. Non-dimensionalization of this SPL correction is implemented in correlations in order to be able to apply it to virtually any given jet size. Superposition with the single jet prediction provides a noise sphere that can be used for environmental noise evaluation. Different jet conditions corresponding to a typical flight profile are computed this way as a test case for producing a full assessment of the noise impact on the community. A similar approach is taken for rectangular jets, concluding with the production of a predicted sound sphere. Finally, a combination of both effects is used to estimate the sound produced by a twin rectangular jet aircraft.