CAREER: Understanding the Exceptional Near-Field Auditory System of the Aye-Aye, One of the Most Unusual Primates in the World

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Over the past 50 million years, the near-field auditory system of aye-ayes, one of the most unique and endangered primates in the world, has evolved to perform an exceptional foraging behavior called tap-scanning. As the aye-aye moves along the surface of a tree, it taps the wood with its unusual middle finger while keeping its nose near the tree’s surface and its large ears bent forward to detect deep cavities in tree bark that contains the worms they eat. This behavior is very similar to what is done in nondestructive evaluation (NDE), a process where an active acoustic wave is generated and the response from a material (e.g., echo) is used to characterize material properties as well as to detect and evaluate defects (e.g., cavities). The aye-aye’s tap-scanning behavior is unique, making it particularly valuable for creating new NDE technologies. The main goal of Faculty Early Career Development (CAREER) research is to understand the exceptional near-field acoustic-based sensing and detection capabilities of aye-ayes, inspiring the creation of new NDE methods. This grant will help support research that will provide a foundation for developing bio-inspired NDE methods, both promoting science and ensuring the safety of our nation’s aging infrastructures. Reliable NDE methods are needed to inspect aging structures, such as bridges, pipelines, power plants, and aircrafts, as well as provide quality control assessments for complex manufactured components. Therefore, this research will benefit both the U.S. economy and promoting the safety of U.S. society by circumventing catastrophic failures of critical aging infrastructures. The principal hypothesis of this research is that the exceptional near-field auditory system of aye-ayes has resulted from two marvelous adaptations: (i) shape and morphology of the aye-aye’s pinnae, ear canals, and head have adapted to enhance the noise reduction and reception of sound reflected from tapping and increase the near-field acoustic beam resolution and (ii) morphological features of the aye-aye’s middle finger have adapted to provide unique acoustic cues during tap-scanning. To test these hypotheses, the research team will perform bio-mimetic and numerical studies. First, a robotic platform will be used to mimic the aye-aye’s middle finger during tap-scanning. The effects of the pinna, head, and ear canal in enhancing the aye-aye’s acoustic near-field sensing will be evaluated experimentally. Second, finite element models will be used to numerically analyze the acoustic field of the aye-aye’s auditory system. Finally, a bio-inspired tap-scanner will be designed and manufactured to be used to inspect composite materials.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.