Advantages of Fluctuating Noise for Measuring Speech Intelligibility in Listeners With Hearing Loss
Measures of speech intelligibility in noise show limited correspondence with difficulties people with hearing loss report from daily life. This mismatch suggests that standard measurement conditions do not sufficiently capture aspects that are relevant for speech perception, such as dip listening and spatial release from masking. In the present study we developed and evaluated a test condition that incorporates these aspects and compared it with a standard condition. Speech intelligibility was measured in 100 participants with normal hearing (NH, N=17) and hearing loss (HL, N=83) ranging from mild to severe. Measurements were conducted using the German matrix sentence test (OLSA) in the standard condition with frontal presentation of stationary noise co-located with the target speech, and the proposed condition with fluctuating, speech-like maskers spatially separated (±60°) from the target. Stimuli were presented via headphones using virtual acoustics. Tests were performed unaided and with individualized amplification. The proposed condition revealed reduced speech intelligibility also for listeners with HL that showed close-to-normal speech intelligibility in the standard condition. With individualized amplification, more listeners with HL showed reduced speech intelligibility compared to NH listeners than in the standard condition. Benefit of amplification varied widely across individuals with similar hearing thresholds, with some listeners showing little or no benefit. The advantages of the proposed condition were driven by masker fluctuations rather than by spatial separation of sound sources. These findings demonstrate that speech intelligibility measurements incorporating fluctuating maskers provide potentially relevant information beyond standard assessments and can support a more individualized assessment of hearing loss.