Improving the noise insulation performance of vibro-acoustic metamaterial panels through multi-resonant design

In the search for lightweight solutions with favourable noise and vibration attenuation, locally resonant vibro-acoustic metamaterials have emerged as a promising candidate due to their stop band behaviour. When used in a sound transmission context, vibro-acoustic metamaterial panels allow to greatly improve the acoustic insulation in a targeted frequency range. However, their peak insulation is typically followed by a strong insulation dip, which hampers their broad applicability. Recently, a dip reduction concept was proposed to reduce this insulation dip using multiple resonances. Although promising, this concept has not yet been demonstrated on a realizable metamaterial panel of representative dimensions. Therefore, this work extends and demonstrates the concept of dip reduction to address the sound insulation dip of a realizable metamaterial panel, while preserving peak insulation performance and total mass addition. To this end, a design framework is presented based on lumped parameter and finite-element model optimizations to efficiently achieve practically realizable dip-reduced metamaterial panel designs. A multi-resonant metamaterial panel is realized and its acoustic insulation performance compared to a conventional metamaterial panel of similar total mass. Acoustic insertion loss measurements demonstrate a clearly improved insulation dip, while peak insulation performance is preserved.