Ambulatory Phonation Monitoring in Prelingual and Postlingual Deaf Patients after Cochlear Implantation

Hearing loss is known to play a fundamental role in voice production due to a lack of auditory feedback. In this study, we evaluated both fundamental frequency (F0) and loudness of voice on adult deaf patients subjected to cochlear implantation, and we analyzed these results according to the prelingual or postlingual onset of the deafness.

The study population, balanced in terms of sex, consisted of 32 adults who had undergone cochlear implantation due to severe or profound bilateral hearing loss (16 with prelingual deafness and 16 with postlingual deafness) and their outcomes were compared with a control group of 32 normal hearing (NH) subjects. All subjects were asked to utter the sustained vowel /a/ for at least 5 s and then to read an Italian phonetically balanced text. Voice recordings were performed by means of an ambulatory phonation monitoring (APM 3200). Measurements were performed without cochlear implant (CI), then with CI switched on, both in quiet condition and with background noise.

Compared to NH subjects, deaf individuals were overall characterized by higher F0 and loudness values, especially in the vowel task than the reading. In the sustained vowel task, no patients demonstrated significant voice changes after switching on the CI; contrarily, in the reading task, the use of the CI reduced both loudness and F0 up to values comparable to NH subjects, although only in males. There was no significant difference in speech parameters between prelingual and postlingual deafness, although overall lower values were evident in case of postlingual deafness. The use of the CI showed a significant reduction of F0 in males with postlingual deafness and of loudness, both for patients with prelingual and postlingual deafness. Finally, there was a positive correlation between postoperative hearing thresholds and overall speech loudness, highlighting how subjects with better hearing outcomes after CI positioning generally speak with a lower loudness and therefore a reduced vocal effort and load.

We found similar speech performances between prelingual and postlingual deafness, both in the vowel /a/ phonation and in the reading, providing a further suggestion that prelingual adult patients may benefit from cochlear implantation in phonation as well, in addition to the known excellent hearing outcomes. Overall, these results highlight the ability of the CI to adjust in everyday speech certain phonatory aspects such as F0 and loudness by restoring the auditory feedback.