Ultrasonographic measurement of cricothyroid space in speech

The physiological background of sentence declination (fundamental frequency, F0, drop) was studied using ultrasound (US) examination of the cricothyroid (CT) space. The US probe was placed anteriorly in the region of middle cricothyroid ligament. The echoes caused by the antero-inferior edge of thyroid and antero-superior edge of the cricoid cartilages were used as points of measurement. The test utterances consisted of threeand five-word sentences. F0, sound level and CT space were measured from recordings. F0 declination and CT space widening showed a phase relationship. E.g., in a long sentence in which the F0 declined from 194 Hz to 85 Hz the CT space change was 4 mm (from 0.83 cm to 1.25 cm). The correlation between the F0 declination and CT space was r=-0.85. The main pitch regulating system connected with CT joint movements seems to contribute to sentence declination production. These biomechanical events can be monitored using the US method.