Voice is the production of a vibrating tone through the vibration of the vocal folds under pulmonary airflow. The glottis is the space between the vocal folds. Phonation is produced through the myoelastic aerodynamic theory, which takes into account the actions of muscles, tissue elasticity, and aerodynamic (airflow) principles. Fundamental frequency is the frequency of vibration of a talker’s vocal folds (as distinguished from other frequencies in speech). An individual’s “normal” fundamental frequency is called their modal frequency. Voice onset time (VOT) is the time (duration) between the release of a plosive and the start (onset) of voicing in the following segment. The vocal folds are complex anatomical structures involving superficial and deep layers; this structure influences the nature of vocal fold vibration and the mucosal wave. In order to explain and illustrate the complex vibration, the two-mass model and the cover--body model are used. Whisper and nasality are phenomena that are counted under the heading "voice" by some authors.

This chapter explores the contributions of two minoritized indigenous languages of Brazil, Maxakalí and Kaingang, to representations of nasality gestures akin to musical scores, as well as the right way to frame the universality of the kinship terms (and ideal universal syllables)' mama’ and ‘papa’ in light of a phonetic model called Enhancement Theory. These languages have either the consonants /m/ and /p/, but not /b/, or /b/ and /p/, but not /m/, and the allophonic environments in which this available phonetic space is used are organized around perceptual and articulatory optimization.