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
Origin of speech rare. Another objection is that in the view of most scholars, speech as we know it emerged relatively late in human evolution, roughly contemporaneously with the emergence of "Homo sapiens." A development as complex as the reconfiguration of the human vocal tract would have required much more time, implying an early date of origin. This discrepancy in timescales undermines the idea that human vocal flexibility was "initially" driven by selection pressures for speech. At least one orangutan has demonstrated the ability to control the voice box. To lower the larynx is to increase the length of the vocal tract, in