Acoustic camouflage: moth wings as metasurface provide bimodal stealth against bat biosonar

声学伪装：飞蛾翅膀作为超表面提供针对蝙蝠生物声纳的双模式隐形

• 批准号: 2266082
• 金额: --
• 依托单位: University of Bristol
• 依托单位国家: 英国
• 项目类别: Studentship
• 财政年份: 2019
• 资助国家: 英国
• 起止时间: 2019 至 无数据
• 项目状态: 已结题
• 来源: https://gtr.ukri.org/projects?ref=studentship-2266082
• 关键词: Acoustic; camouflage; moth; wings; metasurface

Acoustic camouflage: moth wings as metasurface provide bimodal stealth against bat biosonar. Many moths have ultrasound-sensitive ears that detect echolocating bats. Moths without ears could gain protection by stealth acoustic camouflage, absorbing rather than reflecting sound. We found that body fur (Neil et al. subm) and wing scales (Neil et al. in prep) of moths but not butterflies absorbs bat biosonar. Thick body fur is a porous absorber outperforming technical solutions. Aerodynamic constraints render the scale layer on wings too thin (<1/10th of wavelength) for porous absorption requiring resonant functionality. We found individual moth scales are resonant absorbers (Shen et al, under review at PNAS) achieving broadband metasurface functionality (Shen et al, in prep) with implications for ultrathin and lightweight solutions for building acoustics. Stealth camouflage is only adaptive in flight though. Frequently, moths are resting on substrates from which bats glean them. High absorption lets resting moths stand out as a non-reflective 'black spot', while matching substrate reflectivity would provide camouflage. We believe that the resonant wing absorber offers both functionalities - being highly absorptive in flight and highly reflective on a substrate, by exploiting the viscoelastic boundary layer that covers every solid surface. Moths would only need to address their wings to their resting substrate, and many species (e.g. Geometridae) do exactly that. In this interdisciplinary project into biological metasurfaces, we will confirm and quantify that moth wings have bimodal resonant functionality.

声学伪装：蛾翼作为超表面提供双模态隐身对抗蝙蝠生物声纳。许多飞蛾有超声波敏感的耳朵，可以探测到回声定位的蝙蝠。没有耳朵的飞蛾可以通过隐形声学伪装获得保护，吸收而不是反射声音。我们发现飞蛾的体毛（尼尔等人subm）和翅膀鳞片（尼尔等人在准备）而不是蝴蝶吸收蝙蝠生物声纳。厚厚的体毛是一个多孔吸收优于技术解决方案。空气动力学的限制使得机翼上的氧化皮层太薄（<波长的1/10），而不能进行需要谐振功能的多孔吸收。我们发现个别蛾鳞片是共振吸收器（Shen等人，正在PNAS审查），实现宽带元表面功能（Shen等人，准备），这对建筑声学的轻量化和轻量化解决方案有影响。隐形伪装只适用于飞行。飞蛾经常栖息在蝙蝠收集它们的基质上。高吸收率使休眠的飞蛾成为不反光的“黑点”，而匹配的基质反射率则可以提供伪装。我们相信，共振翼吸收器提供了两种功能-在飞行中高度吸收和在基底上高度反射，通过利用覆盖每个固体表面的粘弹性边界层。蛾只需要将它们的翅膀放在它们的休息基质上，许多物种（例如Geometridae）正是这样做的。在这个跨学科的生物超颖表面项目中，我们将确认和量化蛾翅膀具有双峰共振功能。