Free-field evoked auditory brainstem responses in cochlear implant users

Extending Subcortical EEG Responses to Continuous Speech to the Sound-Field

The auditory brainstem response (ABR) is a valuable clinical tool for objective hearing assessment, which is conventionally detected by averaging neural responses to thousands of short stimuli. Progressing beyond these unnatural stimuli, brainstem responses to continuous speech presented via earphones have been recently detected using linear temporal response functions (TRFs). Here, we extend earlier studies by measuring subcortical responses to continuous speech presented in the sound-field, and assess the amount of data needed to estimate brainstem TRFs. Electroencephalography (EEG) was recorded from 24 normal hearing participants while they listened to clicks and stories presented via earphones and loudspeakers. Subcortical TRFs were computed after accounting for non-linear processing in the auditory periphery by either stimulus rectification or an auditory nerve model. Our results demonstrated that subcortical responses to continuous speech could be reliably measured in the sound-field. TRFs estimated using auditory nerve models outperformed simple rectification, and 16 minutes of data was sufficient for the TRFs of all participants to show clear wave V peaks for both earphones and sound-field stimuli. Subcortical TRFs to continuous speech were highly consistent in both earphone and sound-field conditions, and with click ABRs. However, sound-field TRFs required slightly more data (16 minutes) to achieve clear wave V peaks compared to earphone TRFs (12 minutes), possibly due to effects of room acoustics. By investigating subcortical responses to sound-field speech stimuli, this study lays the groundwork for bringing objective hearing assessment closer to real-life conditions, which may lead to improved hearing evaluations and smart hearing technologies.

Auditory Skills as a Predictor of Rater Reliability in the Evaluation of Vocal Quality

OBJECTIVE

To determine whether an association exists between auditory skills and the reliability of judgments of the vocal deviation grade and the degrees of roughness and breathiness and to evaluate whether these skills are predictive of interrater reliability in auditory-perceptual evaluations.

METHODS

The sample consisted of 20 speech-language pathology students without previous training in auditory-perceptual evaluation. The students underwent a basic audiological evaluation and a central auditory processing evaluation. They then participated in two auditory-perceptual evaluation sessions assessing the general grade (GG) and the degrees of roughness and breathiness of 44 samples of sustained vowel production with the presence or absence of dysphonia. For statistical analysis, the intraclass correlation coefficient (ICC) and a beta regression model were used.

RESULTS

A difference was found in the average ICCs of the GG parameter between listeners with high and low temporal resolution and binaural interaction skills. Temporal resolution skills and binaural interaction affected the ICC of listeners in the GG evaluation, reducing the likelihood of reliability by 2.8 and 3.6 times, respectively.

CONCLUSION

An association exists between temporal resolution skills and binaural interaction and the reliability of listeners in evaluations of vocal deviation severity. Listeners with low levels of these skills show less reliability in evaluations of the severity of vocal deviation. In addition, temporal resolution and binaural interaction are predictors and explain 42.7% of the variability in the reliability of evaluations of vocal deviation severity.