Identifying Subclinical Hearing Loss: Extended Audiometry and Word Recognition in Noise

Normal-hearing people often have complaints about the ability to recognize speech in noise. Such disabilities are not typically assessed with conventional audiometry. Suprathreshold temporal deficits might contribute to reduced word recognition in noise as well as reduced temporally based binaural release of masking for speech. Extended high-frequency audibility (>8 kHz) has also been shown to contribute to speech perception in noise. The primary aim of this study was to compare conventional audiometric measures with measures that could reveal subclinical deficits.

Conventional and extended high-frequency audiometry was done with 119 normal-hearing people ranging in age from 18 to 72. The ability to recognize words in noise was evaluated with and without differences in temporally based spatial cues. A low-uncertainty, closed-set word recognition task was used to limit cognitive influences.

In normal-hearing listeners, word recognition in noise ability decreases significantly with increasing pure-tone average (PTA). On average, signal-to-noise ratios worsened by 5.7 and 6.0 dB over the normal range, for the diotic and dichotic conditions, respectively. When controlling for age, a significant relationship remained in the diotic condition. Measurement error was estimated at 1.4 and 1.6 dB for the diotic and dichotic conditions, respectively. Controlling for both PTA and age, EHF-PTAs showed significant partial correlations with SNR50 in both conditions (ρ = 0.30 and 0.23). Temporally based binaural release of masking worsened with age by 1.94 dB from 18 to 72 years old but showed no significant relationship with either PTA.

All three assessments in this study demonstrated hearing problems independently of those observed in conventional audiometry. Considerable degradations in word recognition in noise abilities were observed as PTAs increased within the normal range. The use of an efficient words-in-noise measure might help identify functional hearing problems for individuals that are traditionally normal hearing. Extended audiometry provided additional predictive power for word recognition in noise independent of both the PTA and age. Temporally based binaural release of masking for word recognition decreased with age independent of PTAs within the normal range, indicating multiple mechanisms of age-related decline with potential clinical impact.