An acoustic analysis of the nasal electrolarynx in healthy participants

The nasal electrolarynx (NEL) is an innovative device that assists patients without vocal folds or under endotracheal intubation in producing speech sounds. The NEL has a different path for acoustic wave transmission to the traditional electrolarynx that starts from the nostril, passes through the nasal cavity, velopharyngeal port, and oral cavity, and exits the lips. There are several advantages to the NEL, including being non-handheld and not requiring a specific “sweet spot.” However, little is known about the acoustic characteristics of the NEL. This study investigated the acoustic characteristics of the NEL compared to normal speech using ten participants involved in two vowel production sessions. Compared to normal speech, NEL speech had low-frequency deficits in the linear predictive coding spectrum, higher first and second formants, decreased amplitude of the first formant, and increased amplitude of the nasal pole. The results identify the general acoustic features of the NEL, which are discussed using a tube model of the vocal tract and perturbation theory. Understanding the acoustic properties of NEL will help refine the acoustic source and speech recognition in future studies.