Patterns of Aided Loudness Growth in Experienced Adult Listeners with Early-Onset Severe-Profound Hearing Loss.

Abstract

Individuals with early-onset severe-profound bilateral hearing loss (S/PHL) manifest diverse levels of benefit and satisfaction with hearing aids (HAs), even with prescriptive HA fitting. Such fittings incorporate normal loudness values, but little is known about aided loudness outcomes in this population and how those outcomes affect benefit or satisfaction. To describe aided loudness growth and satisfaction with aided listening in experienced adult HA users with S/PHL. The Contour Test of loudness perception was administered to listeners with S/PHL in the aided sound field using broadband speech, band-limited speech, and warble tones. Patterns and slopes of resultant loudness growth functions were referenced to sound field results from listeners with normal hearing (NH). S/PHL listeners also rated their aided listening satisfaction. It was expected that (1) most S/PHL listeners would demonstrate steeper than normal aided loudness growth, (2) loudness normalization would be associated with better high-frequency detection thresholds and speech recognition, and (3) closer approximation to normal would yield greater satisfaction. Participants were paid college-student volunteers: 23 with S/PHL, long-term aided listening experience, and new HAs; 15 with NH. Participants rated loudness on four ascending runs per stimulus (5-dB increments) using categories defined in 1997 by Cox and colleagues. The region between the 10th and 90th percentiles of the NH distribution constituted local norms against which location and slope of the S/PHL functions were examined over the range from Quiet to Loud-but-OK. S/PHL functions were categorized on the basis of their configurations (locations/slopes) relative to the norms. Pattern of aided loudness was normalized or within 5 dB of the normal region on 37% of trials with sufficient data for analysis. Only one of the 23 S/PHL listeners did not demonstrate Normal/Near-normal loudness on any trials. Four nonnormal patterns were identified: Steep (recruitment-like; 38% of trials); Shifted right, with normal growth rate (10%); Hypersensitive, with most intensities louder than normal (10%); and Shallow, with decreasing growth rate (7%). Listeners with high-frequency average thresholds above 100 dB hearing loss or no phonemic-based speech-discrimination skill were less likely to display normalized loudness. Slope was within norms for 52% of S/PHL trials, most also having a Normal/Near-normal growth pattern. Regardless of measured loudness results, all but four listeners with S/PHL reported satisfactory hearing almost always or most of the time with their HAs in designated priority need areas. The variety of aided loudness growth patterns identified reflects the diversity known to characterize individuals with early-onset S/PHL. Loudness rating at the validation stage of HA fit with these listeners is likely to reveal nonnormal loudness, signaling need for further HA adjustment. High satisfaction, however, despite nonnormal loudness growth, suggests that listeners with poor auditory speech recognition may benefit more from aided loudness that supports pattern perception (via the time-intensity waveform of speech), different from most current-day prescription fits.