'However, no direct evidence exists as to if and how laryngeal and ventricular structures can vibrate to produce sound in bats due to challenges of imaging the vocal folds in vivo at the extremely high speeds required.

Here, we test the hypothesis that specialization of different laryngeal structures supports the extreme frequency range of FM bats. We test this hypothesis in Daubenton’s bats (Myotis daubentonii) that have an extreme 77 octave fo range from 1 to 95 kHz '

https://journals.plos.org/plosbiology/article?id=10.1371/journal.pbio.3001881