Integrating Flowmeter for Measuring Unimpaired Oral and Nasal Airflow

The integrating flowmeter is designed to measure unimpaired oral and nasal airflow during speech. The flow fields (oral and nasal) are sampled by two independent arrays of warmwire velocity sensors. By adding linearized indications of these velocity samples, oral and nasal flows are determined. A desired frequency response of 250 Hz is achieved by using short pieces of 12.7-¿ platinum wire as sensors. Each sensor is maintained at a relatively constant temperature by means of feedback control. An operating temperature of 200 °C is used to minimize error caused by small changes in temperature of the exhaled air. Calibration was established by comparing measurements of vital capacity made using the integrating flowmeter and a wet spirometer. Results obtained yielded an oral flow calibration of 1250 ml/s.V, with a standard deviation of 188 ml/s.V over the normal range of airflow (0 to 1200 ml/s). Because of inadequate sampling, nasal flow is measured with less accuracy. Some of the difficulties in recording airflow in free field during speech are discussed. Emphasis is given to the value of such recordings in speech research.