Obstruent Obstruent An obstruent is a speech sound such as , , or that is formed by "obstructing" airflow. Obstruents contrast with sonorants, which have no such obstruction and so resonate. All obstruents are consonants, but sonorants include both vowels and consonants. Obstruents are subdivided into plosives (oral stops), such as , with complete occlusion of the vocal tract, often followed by a release burst; fricatives, such as , with limited closure, not stopping airflow but making it turbulent; and affricates, which begin with complete occlusion but then release into a fricative-like release, such as . Obstruents are prototypically voiceless, but
Speech synthesis specific usage domains, the storage of entire words or sentences allows for high-quality output. Alternatively, a synthesizer can incorporate a model of the vocal tract and other human voice characteristics to create a completely "synthetic" voice output. The quality of a speech synthesizer is judged by its similarity to the human voice and by its ability to be understood clearly. An intelligible text-to-speech program allows people with visual impairments or reading disabilities to listen to written words on a home computer. Many computer operating systems have included speech synthesizers since the early 1990s. A text-to-speech system (or "engine") is composed