Auditory mechanics in a bush-cricket: direct evidence of dual sound inputs in the pressure difference receiver

Thorin Jonsson, Fernando Montealegre-Z, Carl D Soulsbury, Kate A Robson Brown, Daniel Robert

Research output: Contribution to journalArticle (Academic Journal)peer-review

20 Citations (Scopus)
261 Downloads (Pure)


The ear of the bush-cricket, Copiphora gorgonensis, consists of a system of paired eardrums (tympana) on each foreleg. In these insects, the ear is backed by an air-filled tube, the acoustic trachea (AT), which transfers sound from the prothoracic acoustic spiracle to the internal side of the eardrums. Both surfaces of the eardrums of this auditory system are exposed to sound, making it a directionally sensitive pressure difference receiver. A key feature of the AT is its capacity to reduce the velocity of sound propagation and alter the acoustic driving forces at the tympanum. The mechanism responsible for reduction in sound velocity in the AT remains elusive, yet it is deemed to depend on adiabatic or isothermal conditions. To investigate the biophysics of such multiple input ears, we used micro-scanning laser Doppler vibrometry and micro-computed X-ray tomography. We measured the velocity of sound propagation in the AT, the transmission gains across auditory frequencies and the time-resolved mechanical dynamics of the tympanal membranes in C. gorgonensis Tracheal sound transmission generates a gain of approximately 15 dB SPL, and a propagation velocity of ca 255 m s(-1), an approximately 25% reduction from free field propagation. Modelling tracheal acoustic behaviour that accounts for thermal and viscous effects, we conclude that reduction in sound velocity within the AT can be explained, among others, by heat exchange between the sound wave and the tracheal walls.

Original languageEnglish
Article number20160560
Number of pages11
JournalJournal of the Royal Society Interface
Issue number122
Early online date28 Sept 2016
Publication statusPublished - Sept 2016


  • tympanum
  • sound processing
  • katydid
  • bushcricket
  • sound propagation
  • acoustic trachea


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