Prominence relations in speech are signaled by various ways including such phonetic means as voice fundamental frequency, intensity, and duration. A less studied acoustic feature affecting prominence is the so called voice quality which is determined by changes in the airflow caused by different laryngeal settings. We investigated the changes in voice quality with respect to linguistic prosodic signaling of focus in simple three word utterances. We used inverse filtering based methods for calculating and parametrizing the glottal flow in several different vowels and focus conditions. The results supported our hypothesis -- formed by an earlier study of voice quality changes in running speech -- that more prominent syllables are produced with a less tense voice quality and less prominent ones with a more tense phonation. We provide both physiological and linguistic explanations for the phenomena.