Improving the Sound Transmission Loss of an Aircraft Ceiling Panel by Locally Resonant Metamaterials 2022-01-0960

Lightweight structures and designs have been widely used in a number of engineered structures due to ecological and environmental aspects. Nonetheless, lightweight structures typically experience a reduced noise and vibration reduction performance as a consequence of their increased stiffness-to-mass-ratio. To enhance it, novel low mass and compact countermeasures are often sought to address the challenges of achieving not only a good Noise, Vibrations and Harshness (NVH) reduction performance but also maintaining a lightweight design. Recently, locally resonant metamaterials have emerged and shown potential as a lightweight noise and vibration solution with a superior performance in tunable frequency ranges, known as stop bands i.e. frequency regions where free wave propagation is not allowed. These can be achieved by assembling resonant elements that are tuned to the targeted frequency range onto a host structure. In this paper, the design of a locally resonant metamaterial to improve the acoustic insulation performance of an aircraft ceiling panel is discussed and experimentally verified. The performance of the resonant metamaterial ceiling panel is analyzed by assessing its sound transmission loss response due a diffuse field excitation. The results show that the metamaterial solution is able to strongly improve the acoustic performance of the ceiling panel at the desired frequency range.