Influence of a Mouthpiece on Vocal Function Tests.

A mouthpiece is frequently used when the maximum phonation time (MPT), fundamental frequency (F0) and sound pressure level (SPL) are measured simultaneously with measurements of airflow. The purpose of this study was to determine the influences of the mouthpiece on MPT, F0 and SPL. Forty normal adults (20 males and 20 females) were the subjects. The mouthpiece did not significantly influence MPT. The mouthpiece tended to lower F0 but the influence of the mouthpiece on F0 was small and clinically not important. SPL was significantly affected by the mouthpiece : the SPL value for the softest phonation was greater by 2 dB, that for the loudest phonation was smaller by 8-9 dB, and the SPL range was smaller by 10 dB when the subjects Phonated into the mouthpiece than when phonated without the mouthpiece.