Periodic Reporting for period 1 - InWingSpeak (From Insect Wings to Miniature Loudspeakers - A Bionic Modelling Approach)
Periodo di rendicontazione: 2019-04-01 al 2021-03-31
The goal of this project was to use bioacoustic and state-of-the-art imaging techniques to investigate the morphology, the biomechanical properties and sound-production capabilities of the wings of various cricket and bush-cricket species in detail. By combining computer tomography for the creation of three-dimensional, virtual wings and laser vibrometry that allows to explore the resonances of the real wings, computer models of the wings have been developed. As a result, InWingSpeak produced several computational models of song-producing cricket and bush-cricket wings (see Figure 1). These allowed simulating the song production process and, crucially, the virtual manipulation of wing structures. By studying the effects of changes in wing shape, thickness and material properties, the relationship between wing morphology and emerging resonances and songs was analysed. On the one hand, the resulting knowledge has given insights into the evolution of acoustic communication and insect wings as sound-producing structures. On the other hand, the results also have the potential to inspire and inform engineers in the design of biomimetic miniature loudspeakers for medical devices like hearing aids.
In a further step, the structure and material properties of the virtual models were altered to study the impact of certain morphological changes on the wing vibrations. Alterations were inspired by evolutionary or developmentally conceivable changes like decreasing or increasing membrane and vein thicknesses and changes in wing or vein stiffness (the latter could be influenced by, for example, water content or an animal’s diet). In general, increases in wing stiffness resulted in expected increases in wing resonance (which would lead to higher-pitched song) but changing the stiffness of the veins also showed that the size and location of the vibrations is influenced by this parameter. Similarly, increasing the vein thickness had a pronounced impact on the vibratory behaviour (higher resonances and more confined vibrations). Interestingly, vein morphology seemed to have a greater impact on wing tuning than membrane morphology, suggesting that small changes in wing venation have the potential to produce significant changes in song frequency and amplitude. Further manipulation of vein morphology showed that an inflation of only one central vein (as seen in certain cricket species with unusually high pitch) can change the harmonic composition of the vibrations and thus song frequency and even its “timbre”. Detailed results are currently being prepared for publication in at least two international scientific journals.
Additionally, further investigations of how the morphology of these miniature loudspeakers influences the frequency and amplitude of the ultrasonic songs will provide insights into efficient high-frequency signal generation using small sound sources.