08-17-2017, 12:26 AM
Impedance Glottography
Abstract
Impedance glottography, or electroglottography, is a noninvasive technique for monitoring the variation of the degree of contact between the vibrating vocal cords during voice production. Electrical impedance is sensed using a pair of electrodes placed on either side of the larynx, by injecting a low-level high-frequency current. A wide-band impedance detector circuit has been developed using a precision rectifier based on voltage feedback clamping amplifier and approximately linear-phase lowpass filter. The circuit can be used for obtaining electroglottogram signal for diagnosis of vocal fold disorders.Impedance Glottography is noninvasive measurement of the time variation of the degree of contact between the vibrating vocal folds during voice production. The aspect of contact being measured is called the vocal fold contact area (VFCA). To measure VFCA, the device used is called impedance glottograph. The device is also called electroglottograph or laryngograph. The principle of operation of device, the waveform obtained, an algorithm for determination of pitch period is discussed. EGG waveform for various voice qualities, drawbacks in EGG and various noises present are described. Concept of multichannel EGG and applications of electroglottography are discussed. Various commercial equipment available are compared alongwith the equipment developed by IIT Bombay.