The Mechanics of Insect Audition: Characterisation Modelling and Application

听觉是世界上不同种类动物中最普遍的感觉之一。动物用听觉来交流，倾听危险，帮助寻找午餐。所使用的声音的频率可以变化很大，从鱼类的极低频检测（次声）到蝙蝠用于回声定位和捕食的极高频（超声波）。当然，人类也有听觉，范围从低频到大约20 kHz，尽管随着年龄的增长，我们听到更高频率的能力会下降。然而，通过我们自己的聪明才智，人类已经学会了产生，检测和使用超声波（频率高于我们的频率范围）。我们在许多不同的应用中使用它，包括医学成像、清洁、材料分析和无损检测。人们发明了这种超声波装置，才发现蝙蝠是用超声波来识别和追逐昆虫的，而且许多昆虫的耳朵都被调好了，可以听到蝙蝠试图逃脱成为食物的声音。最近，工程师们开始研究蝙蝠使用超声波的方式。这是因为蝙蝠可以实现比任何人类建造的超声波系统更高的分辨率和灵敏度。工程师们希望能够通过研究蝙蝠使用的技术来改进他们的人工系统。虽然我们对蝙蝠使用的超声波信号了解很多，但我们对蝙蝠的猎物昆虫的听觉系统知之甚少。许多研究已经向我们展示了哪些昆虫对超声波敏感，例如通过观察昆虫在超声波回放时的行为，并从中发现了超声波敏感昆虫中的鼓膜状结构。一些昆虫耳朵的性能也被描述为使用各种技术，包括非常高科技的解决方案，如激光干涉测量法（其中激光用于测量昆虫耳膜对声音的反应）。然而，这些昆虫耳朵内结构的实际机械操作，以及我们对它们如何接收超声波并将其转化为神经细胞可以检测到的振动的理解非常差。这项新的研究将结合工程方法来了解昆虫的超声波敏感耳朵是如何工作的。将测量耳朵中不同结构的机械运动，并描述其尺寸，形状和材料特性。为此，将使用几种技术，包括激光干涉测量法和原子力显微镜（AFM）。AFM通过触摸而不是光来成像表面。它使用一个非常小的，原子般锋利的尖端，在物体表面拖动或敲击。一个记录是由多少这个尖端上升和下降，使我们能够作出一个表面的图像。原子力显微镜的灵敏度足以映射材料表面的原子。除了成像，AFM针尖可以被推入表面，使我们能够测量它的软硬程度。使用这种技术，可以将材料的硬度映射到纳米尺度。一旦所有这些新的信息被收集起来，它将被用来帮助创建耳朵结构的计算机模型。我们可以将模型与我们测量的实际运动进行比较，帮助我们了解耳朵中发生了什么。由此，这些模型为我们提供了一种工具来探索其他耳膜的功能，并进一步了解与其大小，灵敏度和动态范围相关的不同耳朵功能。最后，从这项研究中获得的新知识具有更广泛的应用。回顾一下研究蝙蝠超声波信号的工程师们，这项研究将向我们展示耳朵是如何进化来检测蝙蝠的叫声的。然后，它可以帮助工程师努力改善许多不同领域的人工超声传感器系统，如医学，材料科学和工程。

The sense of hearing is one of the most widespread across the different species of animals in the world. Animals use hearing in communication, to listen for danger and to help find lunch. The frequencies of sound used can vary an enormous amount, from very low frequency detection (infrasound) in fish, to the extremely high frequencies used by bats to echolocate and hunt for prey (ultrasound). Of course humans also have a sense of hearing, ranging from low frequencies up to about 20 kHz, although as we get older, our ability to hear higher frequencies degrades. However, through our own ingenuity humans have learned to generate, detect and use ultrasound (frequencies above our frequency range). We use this in many different applications, including medical imaging, cleaning, material analysis and non-destructive testing. It was only by creating such ultrasound devices that people discovered that bats were using ultrasound to identify and chase insects, and that many insects had ears tuned to listen out for the hunting bats to try and escape becoming a meal. Recently, engineers have started to examine the way bats use ultrasound. This is because the bats can achieve far greater resolution and sensitivity than any human built ultrasound system. The engineers hope to be able to improve their artificial systems by working out what techniques the bats employ. Whilst we know a lot about the ultrasound signals the bats use, we know comparatively little about the hearing systems of the bat's prey; the insects. Many studies have shown us which insects are sensitive to ultrasound, for example by looking at the insect's behaviour when ultrasound is played back to it. And from that, eardrum-like structures in ultrasound sensitive insects were discovered. The performance of some insect ears has also been described using various techniques, including very hi-tech solutions such as laser interferometry (where a laser is used to measure the motion of the insect's eardrum in response to sound). However, the actual mechanical operation of the structures within the ears of these insects, and so our understanding of how they receive ultrasound and translate that to vibrations the nerve cells can detect is very poor. This new research will use a combination of engineering approaches to understand how the ultrasound sensitive ears of insects work. The mechanical motions of different structures in the ears will be measured, with their size, shape and material properties characterised. To do this several techniques will be used including laser interferometry and atomic force microscopy (AFM). An AFM images surfaces by touch, rather than light. It uses a very small, atomically sharp, tip that is dragged, or tapped, across the surface of an object. A record is made of how much this tip goes up and down allowing us to make a surface image. AFM's can be sensitive enough to map the atoms on the surface of a material. As well as imaging, an AFM tip can be pushed into a surface, allowing us to measure how soft or hard it is. Using this technique it's possible to map the stiffness of a material down to nanometre scales. Once all this new information is collected it will be used to help create computer models of the ear structures. We can compare the models with the actual motions we measure, helping us to understand what is happening in the ear. From this, the models provide us with a tool to explore the capabilities of other eardrums, and further our understanding of the different ear capabilities relating to their size, sensitivity and dynamic range. Finally, the new knowledge from this research has broader applications. Looking back to the engineers working on bat ultrasound signals, this research will show us how the ears that have evolved to detect the bat's calls operate. It may then help engineers striving to improve artificial ultrasound sensor systems across many different fields such as medicine, material science and engineering.