Aircraft Supplemental Cooling System Noise Propagation and Radiation: Comparisons between Acoustics Numerical Modeling and Testing

Abstract

Aircraft ramp noise continues to be an important issue for servicing personnel and airport communities. Reduction of aircraft ramp noise requires attention to a number of noise generating systems that are operational during aircraft servicing. The ramp noise contribution from a system known as the Supplemental Cooling System is evaluated numerically and experimentally. Fan noise generated by this system radiates externally through highly three-dimensional inlet and outlet ducting. Meeting aggressive aircraft ramp noise targets requires that acoustic treatment be designed and applied to the inlet and outlet ducts to attenuate the fan noise. Airbus France’s ACTIPOLE solver which uses a Fast Multipole Boundary Element methodology is used to numerically predict the attenuation provided by the acoustic treatment and the directivity of the radiated sound field. Rig testing is carried out to measure the noise level and directivity of the supplemental cooling system, and quantify the attenuation provided by the duct acoustic treatment. Comparisons between predictions and measurements demonstrate that the acoustic treatment insertion loss and the directivity of the sound field radiated from the inlet and outlet ducts can be well predicted for such systems. Thus, reliable and validated prediction procedures are available to design and optimize acoustic treatment packages for these aircraft systems.