Tympanal travelling waves in migratory locusts

J.F.C. Windmill, M. Göpfert, D. Robert

Research output: Contribution to journalArticlepeer-review

55 Citations (Scopus)


Hearing animals, including many vertebrates and insects, have the capacity to analyse the frequency composition of sound. In mammals, frequency analysis
relies on the mechanical response of the basilar membrane in the cochlear duct. These vibrations take the form of a slow vibrational wave propagating along the basilar membrane from base to apex. Known as von Békésy’s travelling wave, this wave displays amplitude maxima at frequency-specific locations along the basilar membrane, providing a spatial map of the frequency of sound – a
tonotopy. In their structure, insect auditory systems may not be as sophisticated as those of mammals, yet some are known to perform sound frequency analysis. In the desert locust, this analysis arises from the mechanical properties of the tympanal membrane. In effect, the spatial decomposition of incident sound into discrete frequency components involves a tympanal travelling wave that
funnels mechanical energy to specific tympanal locations, where distinct groups of mechanoreceptor neurones project. Notably, observed tympanal deflections differ from those predicted by drum theory. Although phenomenologically equivalent, von Békésy’s and the locust’s waves differ in their physical implementation. von Békésy’s wave is born from interactions between the
anisotropic basilar membrane and the surrounding incompressible fluids, whereas the locust’s wave rides on an anisotropic membrane suspended in air. The locust’s ear thus combines in one structure the functions of sound
reception and frequency decomposition.
Original languageEnglish
Pages (from-to)157-168
Number of pages12
JournalJournal of Experimental Biology
Publication statusPublished - 2005


  • bioacoustics
  • frequency detection
  • hearing
  • travelling wave
  • tympanum
  • locust


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