Comparing sound field audiometry and free field auditory steady state response in the verification of hearing aid fitting in adults

Abstract Objectives: The aim of this work was to establish hearing aid (HA) functional gain measurements using free field (FF) auditory steady-state response (ASSR) and to compare and correlate sound field (SF) versus ASSR functional gain and unaided and aided hearing thresholds in order to assess the reliability of FF ASSR as an objective tool for the verification of HA fitting. Participants and methods: This study was conducted on 20 HA user adults with a mean age of 57.09±14.79 years. For each patient, the following were administered: history taking, basic audiological evaluation including pure tone audiometry and immittancemetry, unaided and aided SF audiometry thresholds, and unaided and aided FF ASSR thresholds. The results obtained were then compared. In addition, correlation studies between all the obtained results were carried out. Results: A highly significant difference was found at 500 Hz only between the SF hearing thresholds and the FF ASSR thresholds among the unaided patients at the four test frequencies (500–4000 Hz). Similarly, aided SF and FF ASSR hearing thresholds showed a statistically significant difference only at 500 Hz. The results of correlation coefficient showed that unaided SF and FF ASSR thresholds were positively significantly correlated at 2 and 4 kHz. In addition, aided SF and FF ASSR thresholds were positively significantly correlated at 1 and 2 kHz. Comparison between the functional gain obtained using both SF and FF ASSR tests showed that there was a highly significant difference only at 4000 Hz. Conclusion: SF audiometry and FF ASSR unaided and aided thresholds showed very similar results and this indicates that ASSR may be a good alternative method for the measurement of hearing level in infants and children, for whom pure tone audiometry is not possible. FF ASSR appears to be a reliable procedure for the verification of HA fitting and can be used to assess functional gain in difficult-to-test populations and children. Future research on the effect of the electroacoustic characteristics of HAs on aided FF ASSR thresholds is recommended. © 2012, The Egyptian Oto - Rhino - Laryngological Society.