Benefit from non-linear frequency compression hearing aids in a clinical setting: The effects of duration of experience and severity of high-frequency hearing loss

Abstract

Objectives: To determine whether non-linear frequency compression (NLFC) is effective for hearing-impaired adults in a clinical setting. To determine whether benefit from NLFC is related to duration of NLFC experience or severity of high-frequency hearing loss. Design: Participants were fitted with Phonak frequency compression hearing aids as part of their standard clinical care, using the manufacturer's default fitting settings. Participants had been using NLFC for between 1 and 121 weeks at the time of testing. Speech recognition thresholds in noise and consonant recognition in quiet were measured with and without NLFC enabled. Study sample: Forty-six experienced adult hearing-aid users. Results: Consonant recognition in quiet, but not speech recognition in noise was significantly better with NLFC enabled. There was no significant correlation between duration of frequency compression experience and benefit. Benefit for consonant recognition was negatively correlated with mean audiometric thresholds from 2–6 kHz. Conclusions: NLFC was beneficial for consonant recognition but not speech recognition in noise. There was no evidence to support the idea that a long period of acclimatization is necessary to gain full benefit. The relation between benefit and high-frequency thresholds might be explained by the poor audibility of compressed information for some listeners with severe loss.

Key Words::

• Hearing aids
• frequency compression
• acclimatization

Acknowledgements

This work was presented at the British Academy of Audiology Conference (Manchester, 2012). We thank Keith Wilbraham for assistance with hearing-aid testing, and Richard Baker for assistance with data analysis.

Note

Declaration of interest: AD and KM have previously received funding from Phonak (not in connection with the current study). KH and MK report no conflicts of interest.

Notes

1. It should be noted that the latest version of the Phonak fitting software (Target 3.1) prescribes different default values for start frequency and compression ratio. For the most of the audiograms of the participants tested here, the differences were small; there were only four participants where the start frequency changed by 0.4 kHz or more and/or the compression ratio changed by 0.3 or more; these are indicated with an asterisk in Table 2.