Evaluation of non-linear frequency compression hearing aids using speech P1-cortical auditory evoked potential

Abstract

Objective: To investigate the potential effects of frequency lowering technology on outcome measures of hearing aid efficacy. The detection of mid- and high-frequency syllables in children with sensorineural hearing loss (SNHL) fitted with non-linear frequency compression (NLFC) hearing aids was studied using speech P1 cortical auditory evoked potentials (CAEP). Study design: Thirty Arabic speaking children with bilateral high frequency SNH and with a history of regular binaural hearing aid use were included. All children were fitted with binaural Phonak Naida III UP with a NLFC feature. Verification of NLFC was achieved through aided sound field testing and aided speech P1-CAEP recordings. Aided P1-CAEPs were elicited using synthetic speech stimuli ‘da’ and ‘ga’. Fifteen age-matched normal hearing children served as a control group to provide a reference of typically maturing CAEPs without the influence of hearing impairment. Results: NLFC improved aided thresholds in the mid and high frequencies. No statistically significant difference existed between the control and study group in their CAEP responses to the ‘ga’ stimulus in both NLFC-disabled/enabled conditions. The ‘da’ stimulus elicited P1-CAEP in only 27% of the study group with the NLFC disabled condition; this increased to 83% with activation of NLFC. The P1-CAEP latency of the study group was prolonged compared to children of the control group for both stimuli. The presence of P1-CAEP to both ‘ga’ and ‘da’ stimuli was significantly negatively correlated with the age of the child, duration of hearing loss, and duration of hearing aid use. Conclusion: The NLFC significantly improved the audibility of high frequency sounds for children with severe high frequency SNHL. Speech P1-CAEP can be used as an objective validation tool in children to evaluate the benefit from NLFC especially when behavioural aided thresholds are difficult to obtain.