The morphology of the stylohyal-tympanic bone articulation found in laryngeally echolocating 7 bats is highly indicative of a function associated with signal production. One untested hypothesis is that 8 this morphology allows the transfer of a sound signal from the larynx to the tympanic bones (auditory 9 bulla) via the hyoid apparatus during signal production by the larynx. We used µCT data and finite 10 element analysis (FEA) to model the propagation of sound through the hyoid chain into the tympanic 11 bones to test this hypothesis. We modeled sound pressure (dB) wave propagation from the basihyal to the 12 tympanic bones, vibratory behavior (m) of the stylohyal – tympanic bone unit, and the stylohyal and 13 tympanic bones when the stylohyal bone is allowed to pivot on the tympanic bone. Sound pressure wave 14 propagation was modeled using the harmonic acoustics solver in ANSYS and vibratory behavior was 15 modeled using coupled modal and harmonic response analyses in ANSYS. For both analyses (harmonic 16 acoustics and harmonic response), the input excitation on the basihyal and thyrohyals was modeled as the 17 estimated pressure (Pa) imposed by the collision of the vibrating thyroid cartilage of the larynx against 18 these bones during signal production. Our models support the hypothesis that this stereotypical hyoid 19 morphology found in laryngeally echolocating bats can transfer sound to the auditory bullae at an 20 amplitude that is likely heard for the species Artibeus jamaicensis and Rhinolophus pusillus

The 3D models were rendered from micoCT scans and processed in Fusion 360 and SpaceClaim and saved as STL and STEP files.