Complex sentence: Strident vowels (also called sphincteric vowels) are strongly pharyngealized vowels accompanied by (ary) epiglottal trill, where the larynx is raised and the pharynx constricted, so that either the epiglottis or the arytenoid cartilages vibrate instead of the vocal cords.
Split into simpler sentences: Strident vowels (also called sphincteric vowels) are strongly-pharyngealized vowels accompanied by (ary) epiglottal trill, with the larynx being raised and the pharynx constricted. Either the epiglottis or the arytenoid cartilages thus vibrate instead of the vocal cords.