Analyzing Neoglottal Vibration of Cantonese Tracheoesophageal Speech: Preliminary Aerodynamic Study Using Inverse Filtering

Abstract

Objective: Despite the many studies on tracheoesophageal (TE) speech, the actual vibratory characteristics of the neoglottis in TE speech are not known. The present study examined the neoglottal vibratory pattern of Cantonese TE speakers by comparison with the glottal waveform produced by laryngeal speakers. Subjects and Methods: Eight superior TE and 8 laryngeal speakers of Cantonese participated in the study. All speakers were instructed to produce the vowels /i, ᴂ, a, ᴐ, u/ 3 times, and both acoustic and aerodynamic signals were recorded. While the airflow signals were later inverse-filtered to obtain the neoglottal and glottal waveforms, the acoustic signals were analyzed to obtain vowel formants, which were used as inputs to inverse filtering. Aerodynamic parameters including open quotient (OQ), speed quotient (SQ), and area under the curve (AUC) were compared between TE and laryngeal speakers. -Results: Results revealed that TE speakers exhibited comparable OQ and AUC, but significantly reduced SQ when compared with laryngeal speakers. Conclusions: Both inverse-filtered airflow signals associated with TE and laryngeal speech of Cantonese appear to be triangular in shape, indicating the opening, closing and closed phases of the (neo)glottis. However, neoglottal waveforms are highly variable. Such variability and inconsistency in neoglottal waveforms might be related to the lack of complete control over the neoglottis in TE speakers.