ASA 126th Meeting Denver 1993 October 4-8

2aSP10. Measurement accuracy of the Glottal Enterprises pneumotach system.

Ronald C. Scherer Christopher Dromey Chwen-Geng Guo

The Denver Ctr. for the Performing Arts, 1245 Champa St., Denver, CO 80204

An important instrument for measuring airflows in speech is the pneumotach system provided by Glottal Enterprises. Inverse filtering the measured airflow allows the estimation of glottal volume velocity. The face mask (MSIF-2) has numerous wire-meshed holes placed approximately in the plane of the lips. Airflow from the mouth during speech may come out in a directed stream, creating nonuniform flow through the mask and measured pressures (Micro Switch) that do not reflect the correct flow. Results for cylindrical tubes representing mouth openings indicate that the angle of the flow makes a difference: e.g., for a flow of about 700 cc/s projecting upward versus downward at 45-deg angles, the difference in estimated flow is 100--250 cc/s for a small tube opening (0.2 sq cm). The difference is only about 10 cc/s for a medium size mouth opening of 2.0 sq cm. Also, results indicate that equipment drift is a minor concern, flow estimates are negligibly different for the expected range of face protrusions into the mask for the medium mouth opening, and the effects of temperature change were negligible. Results will be discussed relative to the accuracy of flow measures for particular speech and voice sounds.