Dear All, Our recent paper on toothed whale sound production may be of interest to some of you. We have sought to address the fundamental questions of 1) how echolocating toothed whales can make 500 clicks per second with air at a 1000 meters depth where air volumes are compressed to less than 1%, and 2) how toothed whales with the same nasal sound source produce can both powerful, high frequency clicks for echolocation and softer, low frequency calls for complex communication? We confirm that toothed whales possess a nasal sound production system driven by air. Loud clicks are made when phonic lips collide after having been forced apart by the airflow. This air-driven, self-sustained oscillation mechanism for sound production is functionally the same as laryngeal and syringeal sound production in other mammals and birds. Acoustic analysis of calls across different toothed whale species shows that vocalizations are produced at different frequency regimes, consistent with tissue vibrations at different registers: just like human vocal folds making the vocal fry, chest and falsetto registers. We conclude that the vocal fry register makes powerful, high frequency echolocation clicks in toothed whales, and the two other registers make softer, more low frequency social calls for mediating complex behavioral interactions via acoustic communication. For both sound types, air can be recycled, allowing for continued sound production during deep dives. The vocal fry register for echolocation uses only very little air per click because the phonic lips only open for about 1 ms, explaining how these apex predators can make the loudest biological sound pressure levels in the animal kingdom at depths of more than 1000 meters. This trick opened the previously unexplored rich food niches of the deep ocean for exploitation by more than 20 species of large toothed whales. The paper can be found here https://www.science.org/doi/10.1126/science.adc9570 If you don't have access, please feel free to write me an email for a pdf. Best peter