Investigation of an extended bandwidth hearing aid on the objective and subjective performance of adults with mild to moderate hearing loss

Abstract

Introduction: Until recently, most conventional hearing aids were only capable of providing usable gain to the ear up to 5-6 kHz. Nowadays, advances in digital signal processing have made it possible to provide a wider band frequency response with smoother, more precise spectral shaping and reduced feedback issues. Several manufacturers have introduced hearing aids which are claimed to provide gain for frequencies up to 10-12 kHz. However there is currently limited evidence and very few independent studies evaluating performance of extended bandwidth hearing aids that have recently become available on the market. Aims: This study investigated a new extended bandwidth hearing aid using objective measures of speech intelligibility and subjective measures of perceptual qualities to find out whether there is a significant benefit of extended bandwidth amplification over standard amplification. Methods: Sixteen adult participants with mild to moderate sensorineural hearing loss were bilaterally fit with a pair of Widex Mind 440 behind-the-ear hearing aids programmed with a standard bandwidth fitting and an extended bandwidth fitting; the latter provided gain up to 10 kHz. For each fitting, and an unaided condition, participants completed two objective measures of aided benefit: the QuickSINTM speech intelligibility in noise test, and the Phonak Phoneme Perception Test (high frequency perception in quiet), and one subjective measure of sound quality. Results: There were no significant differences found between unaided and aided conditions for speech intelligibility in noise scores. For the Phoneme Perception Test, there were significantly lower (improved) detection thresholds at high frequencies (6 kHz and 9 kHz) with the extended bandwidth fitting. Although not statistically significant, participants were able to distinguish between 6 kHz and 9 kHz 50% better with extended bandwidth. No significant difference was found in ability to recognise phonemes in quiet between the unaided and aided conditions when phonemes only contained frequency content less than 6 kHz. However significant benefit was found with the extended bandwidth fitting for recognition of 9 kHz phonemes. Subjective measures revealed no significant difference in sound quality preference between the standard bandwidth and extended bandwidth fittings. Conclusions: This study demonstrated that a pair of currently available extended bandwidth hearing aids was technically capable of delivering high frequency amplification that is both audible and useable to hearing impaired listeners with mild to moderate hearing loss, and was of acceptable sound quality. Further research, particularly field trials, is required to ascertain real-world benefit of high frequency amplification.