Hard of Hearing Listeners Show Rollover at Moderate to High Levels for Speech Materials With and Without Semantic...

At low levels, a level increase typically leads to better speech intelligibility (SI) due to more audibility. At high levels, a level increase can lead to poorer SI and, thus, "rollover." In a previous study conducted with listeners with normal audiometric thresholds, we found rollover with sentences without semantic context but not with semantic context, suggesting that context information can "mask" rollover. Here, we investigated if equivalent results can be found for listeners with elevated audiometric thresholds.

SI scores were measured for two groups of older hard of hearing adults with individual linear amplification. Testing was performed in speech-shaped noise with context-rich and context-free sentences. One group was tested at speech levels of 65 and 75 dB SPL. The other group was tested at a level approximating maximal SI, that is, the individual aided most comfortable level (aMCL) + 10 dB, and at 85 dB SPL. Linear mixed-effects models were used to test for level-dependent changes in SI for the two sentence materials.

Rollover occurred for both groups and sentence materials. For the measurements made at 65 and 75 dB SPL, SI decreased by 7.1% for both sentence materials. For the measurements made at aMCL +10 dB and 85 dB SPL, SI decreased by 9.3% for the context-free sentences and by 10.4% for the context-rich sentences.

Linearly aided hard of hearing listeners show rollover at moderate to high levels for sentence materials with and without semantic context information.