Changing resonator geometry to boost sound power decouples size and song frequency in a small insect

Mhatre, Natasha, Montealegre-Z, Fernando, Balakrishnan, Rohini and Robert, Daniel (2012) Changing resonator geometry to boost sound power decouples size and song frequency in a small insect. Proceedings of the National Academy of Sciences, 109 (22). E1444. ISSN 1091-6490

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Despite their small size, some insects, such as crickets, can produce
high amplitude mating songs by rubbing their wings together. By
exploiting structural resonance for sound radiation, crickets broadcast species-specific songs at a sharply tuned frequency. Such songs enhance the range of signal transmission, contain information
about the signaler’s quality, and allow mate choice. The production
of pure tones requires elaborate structural mechanisms that control and sustain resonance at the species-specific frequency. Tree
crickets differ sharply from this scheme. Although they use a resonant system to produce sound, tree crickets can produce high amplitude songs at different frequencies, varying by as much as an
octave. Based on an investigation of the driving mechanism and
the resonant system, using laser Doppler vibrometry and finite element modeling, we show that it is the distinctive geometry of the
crickets’ forewings (the resonant system) that is responsible for
their capacity to vary frequency. The long, enlarged wings enable
the production of high amplitude songs; however, as a mechanical
consequence of the high aspect ratio, the resonant structures have
multiple resonant modes that are similar in frequency. The drive
produced by the singing apparatus cannot, therefore, be locked
to a single frequency, and different resonant modes can easily be
engaged, allowing individual males to vary the carrier frequency of
their songs. Such flexibility in sound production, decoupling body
size and song frequency, has important implications for conventional views of mate choice, and offers inspiration for the design
of miniature, multifrequency, resonant acoustic radiators.

Keywords:bioacoustics, biological modelling, biomechanics, finite element analysis
Subjects:G Mathematical and Computer Sciences > G430 Computational Science Foundations
C Biological Sciences > C790 Molecular Biology, Biophysics and Biochemistry not elsewhere classified
Divisions:College of Science > School of Life Sciences
ID Code:6261
Deposited On:04 Oct 2012 20:14

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