Horses' whinny unveils a two-tone vocal trick: low rumble and high whistle
Researchers show the horse whinny is produced by two simultaneous sounds: a low-frequency vibration from the vocal folds and a high-pitched whistle created as air passes through laryngeal cartilage. This biphonation—a rare multi-tone vocalization—may convey complex social messages. Endoscopic observations and ex vivo larynx experiments (including helium tests) confirmed the mechanisms, placing horses among a small group of species capable of such vocal tricks.