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在與蝙蝠的超聲波大戰(zhàn)中，飛蛾“隱形”了 新的研究發(fā)現(xiàn)，飛蛾的翅膀能消音。 飛蛾翅膀是一種“超聲學(xué)材料”。來源：Thomas Neil, University of Bristol 蝙蝠能夠利用回聲定位來捕獵佳肴，而飛蛾則常常出現(xiàn)在它們的菜單中。在這場捕食者與獵物的聲學(xué)軍備競賽中，飛蛾也有兩手絕活——準(zhǔn)確地說是“兩翼”絕活：一項新的研究顯示，飛蛾翅膀上的鱗片能夠吸收聲波，尤其是蝙蝠最愛的超聲波。 “飛蛾和蝴蝶的翅膀都被一層層鱗片覆蓋著，這些鱗片由一種叫做甲殼素（chitin）的天然聚合物組成。大多數(shù)昆蟲和甲殼動物的外骨骼中都存在甲殼素?！庇祭锼雇写髮W(xué)（University of Bristol）的托馬斯·尼爾（Thomas Neil）說，一開始，他用聲波對飛蛾的翅膀進(jìn)行轟擊，觀察回彈的情況。 “我們發(fā)現(xiàn)， 被超聲波擊中時飛蛾鱗片會與之共振，共振頻率與蝙蝠用于回聲定位的超聲波頻率幾乎是一致的?！闭駝訉⒊暡ǖ哪芰哭D(zhuǎn)化成了機(jī)械能，這會減弱傳回到蝙蝠的回聲。 “這可能不是巧合。由于具有特定的形狀和大小，這些鱗片的共振頻率恰到好處，讓它們能夠吸收來自狩獵蝙蝠的聲波能量。” 接下來，尼爾和同事對一系列不同鱗片的聲波阻尼性能進(jìn)行了建模。 “飛蛾身上很有趣的一點(diǎn)是，所有的鱗片都有著不同的形狀和大小。我們發(fā)現(xiàn)，每個鱗片的共振頻率都有細(xì)微的差別——合在一起，它們能吸收的（聲波）頻率范圍就很大了?！边@個范圍包括了蝙蝠回聲定位的頻率，尼爾在美國聲學(xué)學(xué)會會議（Meeting of the Acoustical Society of America）上報告了這一發(fā)現(xiàn)。這說明，即使在野外遇到了一大波蝙蝠，飛蛾受到的保護(hù)也應(yīng)該相當(dāng)周全。 不過，這個策略真能奏效嗎……[查看全文] Moths Have an Acoustic Invisibility Cloak to Stay under Bats' Radar Hopkin: Bats use echolocation to hunt for their meals, and moths are often on the menu. But in the acoustic arms race between predator and prey, moths also have a trick or two up their sleeve—or, actually, on their wings, because a new study shows that moth wings are covered with scales that absorb sound, particularly the ultrasonic variety preferred by bats. Thomas Neil: So moth and butterfly wings are covered in layers of scales. These are made of a naturally occurring polymer called chitin, which is a polymer you find in most insect and crustacean exoskeletons. Hopkin: That’s Thomas Neil of the University of Bristol. He started out by bombarding bits of moth wings with sound and seeing what bounced back. Neil: We discovered that moth scales actually resonate in response to being hit with ultrasound. And they resonate at frequencies that pretty much perfectly match the frequencies that bats use for echolocation. Hopkin: That vibration converts sound energy to mechanical energy, which muffles the echo that gets back to the bats. Neil: That probably hasn’t happened by accident, that these scales are such a shape and size that they’re resonating at just the right frequencies that they can absorb sound energy from hunting bats. Hopkin: Next, Neil and his colleagues modeled the sound-dampening capabilities of an array of different scales. Neil: The really cool thing about moths is their scales are all different shapes and sizes. So what we found is that each individual scale will resonate at slightly different frequencies—and that, collectively, they actually absorb a really broadband range of frequencies. Hopkin: That range covers the frequencies of bat echolocation calls—findings Neil presented at the Meeting of the Acoustical Society of America. Neil: So it means that the moths should be pretty well protected from a whole host of bats that they might interact with out in the wild. Hopkin: But does the strategy actually work…[full transcript] “ Neil, T.R., Shen, Z., Robert, D., Drinkwater, B.W. and Holderied, M.W., 2020. Moth wings are acoustic metamaterials. Proceedings of the National Academy of Sciences, 117(49), pp.31134-31141. 封面圖片來源：Pixabay |
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來自： taotao_2016 > 《物理》
