Chamber music: an unusual Helmholtz resonator for song amplification in a Neotropical bush-cricket (Orthoptera, Tettigoniidae)

Jonsson, Thorin and Chivers, Benedict and Robson-Brown, Kate A. and Sarria, Fabio and Walker, Matthew and Montealegre-Z, Fernando (2017) Chamber music: an unusual Helmholtz resonator for song amplification in a Neotropical bush-cricket (Orthoptera, Tettigoniidae). Journal of Experimental Biology, 220 . ISSN 0022-0949

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Animals use sound for communication, with high-amplitude signals being selected for attracting mates or deterring rivals. High amplitudes are attained by employing primary resonators in sound producing structures to amplify the signal (e.g., avian syrinx). Some species actively exploit acoustic properties of natural structures to enhance signal transmission by using these as secondary resonators (e.g., tree-hole frogs). Male bush-crickets produce sound by tegminal stridulation and often use specialised wing areas as primary resonators. Interestingly, Acanthacara acuta, a Neotropical bush-cricket, exhibits an unusual pronotal inflation, forming a chamber covering the wings. It has been suggested that such pronotal chambers enhance amplitude and tuning of the signal by constituting a (secondary) Helmholtz resonator. If true, the intact system – when stimulated sympathetically with broadband sound – should show clear resonance around the song carrier frequency which should be largely independent of pronotum material, and change when the system is destroyed. Using laser Doppler vibrometry on living and preserved specimens, micro computed tomography, 3D printed models, and finite element modelling, we show that the pronotal chamber not only functions as a Helmholtz resonator due to its intact morphology but also resonates at frequencies of the calling song on itself, making song production a three-resonator system.

Additional Information:This paper describes an amazing adaptation of an acoustic insect to amplify sound signals, and make them louder.
Keywords:Acoustic resonator, katydid, bioacoustics, Laser Doppler Vibrometry, finite element modelling, micro computed tomography
Subjects:C Biological Sciences > C770 Biophysical Science
G Mathematical and Computer Sciences > G140 Numerical Analysis
F Physical Sciences > F361 Laser Physics
F Physical Sciences > F380 Acoustics
C Biological Sciences > C340 Entomology
Divisions:College of Science > School of Life Sciences
ID Code:27609
Deposited On:14 Jun 2017 13:48

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