Investigation of Extended Bandwidth Hearing Aid Amplification on Speech Intelligibility and Sound Quality in Adults with Mild-to-Moderate Hearing Loss.

BACKGROUND: Advances in digital signal processing have made it possible to provide a wide-band frequency response with smooth, precise spectral shaping. Several manufacturers have introduced hearing aids that are claimed to provide gain for frequencies up to 10-12 kHz. However, there is currently limited evidence and very few independent studies evaluating the performance of the extended bandwidth hearing aids that have recently become available.

PURPOSE: This study investigated an extended bandwidth hearing aid using measures of speech intelligibility and sound quality to find out whether there was a significant benefit of extended bandwidth amplification over standard amplification.

RESEARCH DESIGN: Repeated measures study designed to examine the efficacy of extended bandwidth amplification compared to standard bandwidth amplification.

STUDY SAMPLE: Sixteen adult participants with mild-to-moderate sensorineural hearing loss.

INTERVENTION: Participants 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.

DATA COLLECTION AND ANALYSIS: For each fitting, and an unaided condition, participants completed two speech measures of aided benefit, the Quick Speech-in-Noise test (QuickSIN™) and the Phonak Phoneme Perception Test (PPT; high-frequency perception in quiet), and a measure of sound quality rating.

RESULTS: There were no significant differences found between unaided and aided conditions for QuickSIN™ scores. For the PPT, there were statistically significantly lower (improved) detection thresholds at high frequencies (6 and 9 kHz) with the extended bandwidth fitting. Although not statistically significant, participants were able to distinguish between 6 and 9 kHz 50% better with extended bandwidth. No significant difference was found in ability to recognize phonemes in quiet between the unaided and aided conditions when phonemes only contained frequency content <6 kHz. However significant benefit was found with the extended bandwidth fitting for recognition of 9-kHz phonemes. No significant difference in sound quality preference was found 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 was both audible and useable to listeners with mild-to-moderate hearing loss. This amplification was of acceptable sound quality. Further research, particularly field trials, is required to ascertain the real-world benefit of high-frequency amplification.