ASSESSMENT OF LARYNGEAL VIBRATORY EVENTS DURING PHONATION IN PATIENTSWITH VOCAL FOLD PARALYSIS USING FAST FOURIER TRANSFORMATION OF ELECTROGLOTTOGRAMS

The electroglottogram (EEG) is known to be related to the motion of vo cal folds. The major hypothesis is that the EGG is related to the area of contact of the vocal folds. EGG is thought to be incapable of meas uring or monitoring non-contact type vibratory events in the larynx. R ecently it was demonstrated by fast Fourier transformation (FFT) analy sis of EGG curves that the resulting EGG can be interpreted as a sum o f a 'laryngeal fundamental with overtones'. This necessitates a new in terpretation of normal EGG waveshape. This study was undertaken to pro ve the hypothesis that (pathological) EGG curves contain information e ven about non-contact type vibratory events in the larynx during phona tion when analyzed by FFT. Patients with vocal fold paralysis were ask ed to phonate sustained vowels (/a/, /e/, /i/, /o/, /u/). Voice sounds and EGG signals were recorded simultaneously, routed to a frequency a nalyzer and subjected to real-time FFT analysis. In all cases original EGG signals would have been classified as pathological. However, in a ll recordings the laryngeal fundamental frequency and - in some patien ts - overtones with their intensities could be extracted and compared to harmonics extracted from voice sound. This is the first report of F FT analysis of EGG signals in patients with vocal fold paralysis. It i s proposed that vocal folds vibratory events may be of non-contact typ e and that they can be monitored by analysis of glottic impedance,