Meeting Abstract
4.3 Friday, Jan. 4 Mechanics of bat vocal folds DUDEK, DM*; GAO, L; LU, H; MUELLER, R; Virginia Tech; Shandong Univ; Shandong Univ; Virginia Tech & Shandong Univ dmdudek@vt.edu
Many bat species emit ultrasonic pulses as part of their active biosonar sensing. These pulses are produced, as in other mammals, through vibrating membranes called vocal folds. However, the performance of bats stands out through a singular combination of four features, namely high output amplitudes, miniaturization, efficiency, and reliability, that vastly outperforms any other solutions found in nature or in man-made technology. Output sound pressure levels as high as three times the human pain threshold have been reported, produced by a vibrating area measuring less than a mm2. Researchers have failed to detect an increase in the energy consumption ascribable to the emission of ultrasonic signals. Hence, bats must be efficient in converting metabolic into ultrasonic energy to an extent that vastly exceeds current technical capabilities, where the production of strong ultrasonic signals requires input powers on the order of 100W. Finally, bats repetitively produce sonar signals for extended periods of time. Nevertheless, their biosonar pulses remain free from the signs of hoarseness that are readily detectable in the voices of other mammals and humans. This indicates the presence of special mechanisms to ensure reliability and repeatability of the signals in bats. To begin to understand this impressive performance, we measured the mechanical properties of vocal folds from the great roundleaf bat, Hipposideros armiger. Compared to similarly sized rats, who emit ultrasound via whistle rather than vocal fold, bat vocal folds are stiffer and show less and slower relaxation processes. Because of all these unique features and the wide performance gap between bat biosonar and ultrasound production by man-made devices, bat biosonar could be a paragon to inspire the design of miniature ultrasonic emitters, enabling miniature active sensing for autonomous systems.
