A general mechanism of air-borne hearing in Recent and early non-tympanate tetrapods

Jakob Christensen-Dalsgaard, Tanya Bojesen Lauridsen, Grace Capshaw, Catherine E. Carr

Research output: Contribution to journalJournal articleResearch


Tetrapod tympanic hearing probably emerged in the Triassic with independent origins in each of the major groups, more than 120 Myr after the water-land transition. During this long period, any auditory sensitivity must have been based on non-tympanic, bone conduction mechanisms. However, ‘bone conduction’ is a non-specific term describing several different modes of vibration that can stimulate the inner ear.

To understand hearing in a non-tympanic ear, we focus on the simplest model: that sound translates the head, i.e., that the head is pushed and pulled by the sound wave, and that this vibration is transduced by the inner ear. Simple translation is the mode of human low-frequency bone conduction sensitivity and translation by underwater sound is also the mode of auditory stimulation for most fishes. It is therefore a straightforward assumption that this may have been the mechanism of hearing in the early tetrapods. According to acoustic theory, the efficiency of translation of an object by sound is determined by its density and ka, the product of the acoustic wavenumber (k) and the radius (a) of the head. Simple finite-element models of translation by sound show that vibration velocities only depend on ka and density (for objects of the same shape and composition) and are almost constant (between 4 and 5 µm/s/Pa depending on shape) for objects with ka
Original languageEnglish
Publication statusIn preparation - 10. May 2022


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