Young healthy adults can hear tones up to at least 20 kHz. However, clinical audiometry, by which hearing loss is diagnosed, is limited at high frequencies to 8 kHz. Evidence suggests there is salient information at extended high frequencies (EHFs; 8 to 20 kHz) that may influence speech intelligibility, but whether that information is used in challenging listening conditions remains unknown. Difficulty understanding speech in noisy environments is the most common concern people have about their hearing and usually the first sign of age-related hearing loss. Digits-in-noise (DIN), a widely used test of speech-in-noise perception, can be sensitized for detection of high-frequency hearing loss by low-pass filtering the broadband masking noise. Here, we used standard and EHF audiometry, self-report, and successively higher cutoff frequency filters (2 to 8 kHz) in a DIN test to investigate contributions of higher-frequency hearing to speech-in-noise perception. Three surprising results were found. First, 74 of 116 “normally hearing,” mostly younger adults had some hearing loss at frequencies above 8 kHz. Early EHF hearing loss may thus be an easily measured, preventive warning to protect hearing. Second, EHF hearing loss correlated with self-reported difficulty hearing in noise. Finally, even with the broadest filtered noise (≤8 kHz), DIN hearing thresholds were significantly better (P < 0.0001) than those using broadband noise. Sound energy above 8 kHz thus contributes to speech perception in noise. People with “normal hearing” frequently report difficulty hearing in challenging environments. Our results suggest that one contribution to this difficulty is EHF hearing loss.
The prevalence of late-diagnosed or often unrecognized hearing loss (HL) is higher in developing countries due to the lack of access to hearing health care services. Due to the importance of hearing screening tests in early diagnosis of HL, development of remotely deliverable screening tests that can detect HL reliably, quickly, and easily provides significant benefits, specifically for underserved population. The purpose of this research is to refine the established English digit triplet test (DTT) to improve detection of high-frequency HL. The sensitivity and specificity of the DTT for detecting high frequency HL will be analyzed for low-pass filtered speech-shaped noise with three different cut-off frequencies (2 kHz, 4 kHz, and 8 kHz). The current study will also replicate previous work showing that speech reception thresholds estimated from the DTT correlate highly with listeners’ pure tone average audiometry. This research should improve the accuracy of convenient, efficient tools for diagnosing HL for millions of people who have limited access to hearing health care.
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