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Abnormal speech processing in frequency regions where absolute thresholds are normal for listeners with
Agnès C Léger1, Brian C J Moore, Christian Lorenzi
1Equipe Audition, Institut d'Etude de la Cognition, École Normale Supérieure, Paris Sciences et Lettres, 29 rue d'Ulm, 75005 Paris, France. agnes.leger@ens.fr
Hearing Research
|October 30, 2012
Summary
Hearing-impaired individuals with normal low-frequency hearing can experience significant speech understanding difficulties. These deficits stem from suprathreshold auditory issues, not just reduced loudness.
Area of Science:
- Audiology
- Speech Perception
- Neuroscience
Background:
- Many individuals with high-frequency hearing loss (HFHL) exhibit normal or near-normal hearing in low and mid-frequency ranges.
- Speech understanding deficits in noise are common, but their origin in individuals with seemingly mild hearing loss is not fully understood.
Purpose of the Study:
- To investigate speech intelligibility in quiet and noise for listeners with HFHL.
- To determine if speech deficits are linked to audibility, outer hair cell function, or aging.
Main Methods:
- Speech-in-quiet and speech-in-noise tests were administered to 26 listeners with HFHL.
- Audiometric thresholds, inter-aural phase sensitivity, otoacoustic emissions (OAEs), and brainstem responses were measured.
- Stimuli focused on low (≤1.5 kHz) and mid (1-3 kHz) frequency regions.
Main Results:
- Approximately 50% of listeners with HFHL showed poor speech intelligibility, even in quiet.
- These deficits were not explained by reduced audibility alone.
- Speech scores correlated with age, audiometric thresholds (low and high frequency), and mid-frequency OAE amplitude, but not inter-aural phase discrimination.
Conclusions:
- Significant speech processing deficits can occur in frequency regions with normal or near-normal hearing in individuals with hearing impairment.
- Outer hair cell damage and aging appear to contribute to these suprathreshold auditory deficits affecting speech understanding.
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