Contribution
Optimal Acoustic Metamaterial Property Determination for the Reduction of Propeller Noise
* Presenting author
Abstract:
Acoustic Metamaterials (AMM) are designed to control, direct, and manipulate sound waves through dissipation, local resonance, and phase shift. AMMs can, for example, be used to mitigate noise to improve acoustic comfort in cars, passenger aircraft, or buildings. This work investigates the noise reduction potential of propeller-driven aircraft noise using AMM. In highly integrated multirotor aircraft configurations, the scattering of propeller noise at the airframe can contribute significantly to the overall aircraft noise emissions. Typically, exterior aircraft noise reductions are attempted through dissipative AMMs that absorb incoming noise. This work uses multi-disciplinary design optimization (MDO) to identify optimal absorption and phase shift properties of the AAM. A numerically efficient medium-fidelity toolchain describing the generation, scattering, and propagation of propeller noise is utilized within the optimization. Using this optimization approach, the AMM properties in different regions close to the propeller are determined such that the overall aircraft sound power level becomes minimal. The phase shift property is shown to be more effective than the absorption property in reducing noise. The results of this work give guidance for the design of aircraft-specific AMM for future noise reduction attempts.