Long-Term Effects of Non-Linear Frequency Compression on Performance of Music and Speech Perception

Objective: Previous studies have already documented improved speech intelligibility and music performance with the use of Nonlinear Frequency Compression (NFC) but as it is widely acknowledged that hearing aid users may gain increasing benefit with longer experience it is interesting to look into long-term effects of this technology. Speech perception benefit with extended use of NFC has been reported for children and cochlear implantees showed a significant improvement in melody recognition after extended use. Aim: The purpose of this study was to determine the long term effect on the perception of music with NFC in adult hearing aid users and whether speech intelligibility in noise changed with extended use of NFC. Design and Sample: As real-life use and experience of NFC hearing aids is necessary to reveal its true potential, the study described in this article was performed roughly three years after the initial study to address any long-term aspects and therefore a comparitive research design was implemented. A subgroup of the participants (n=9) of the study described in Uys, Pottas, Vinck and Van Dijk was recruited to check for their music performance and speech intelligibility after 3 years’ experience with NFC. Results and Conclusion: The results confirm the general observation of increased benefit from the hearing devices when making use of the high-frequency cues provided by NFC. Whereas the majority of parameters describing the subjective perception did not change, those parameters relating to the performance especially melody identification and speech understanding in noise did improve over the longer period. This leads to the conclusion that it is prudent to intensify the evaluation into the long-term effects of NFC technology.