Vocal vibrato has a number of manifestations. Typically vibrato is first thought of as a variation in fundamental frequency (fo), and secondarily as a variation in intensity and sound quality. Other variations that accompany these three types of vibrato include movement of throat structures (changes in larynx height, alterations in arytenoid adduction, pharyngeal wall movement, tongue movement, etc.), and especially muscle contraction variations that accompany all mentioned vibrato types.

Inspiratory or reverse phonation refers to the production of voice when air is inhaled from the mouth and nostrils into the lungs. This way of phonation occurs naturally during laughter, sighs, and crying [1]. It has also been used to achieve special vocal effects by singers, shamans, and ventriloquists, and is common in the vocalizations of other mammals and birds. Furthermore, it is a useful treatment exercise in voice therapy for several voice disorders [2]. However, despite its relevance, few physical studies of inspiratory phonation have been conducted, and its underlying physics still needs further clarification.