Michal Feręczkowski1,2, Benedikte Degn Mikkelsen1, Tobias Neher1,2
1Department of Clinical Research, Faculty of Health Sciences, University of Southern Denmark, Odense, Denmark
2Research Unit for ORL – Head & Neck Surgery and Audiology, Odense University Hospital, Odense, Denmark; University of Southern Denmark, Odense, Denmark
The dependence of speech intelligibility on the presentation level has traditionally been modelled with non-decreasing functions such as sigmoids, for both normal-hearing listeners and listeners with sensorineural hearing loss (SNHL). A performance decrease at high presentation levels – so-called rollover (RO) in the performance-intensity function – has traditionally been interpreted as a sign of retro-cochlear hearing loss. In some recent research studies based on speech stimuli presented at high levels, RO was also observed in young listeners with normal audiograms (NAs), possibly reflecting synaptopathy. Overall, RO measurements could therefore be a useful tool for characterizing suprathreshold hearing abilities in various listener groups. While RO has been observed in a number of studies that employed monosyllabic words or low-context sentences, reports of RO in the recognition of high-context sentences are lacking. Here, we hypothesized that RO presence in the performance-intensity function is related to the amount of context information available in the employed speech material. To test this hypothesis, 22 young NA adults without any self-reported hearing problems were tested at two presentation levels (80 and 95 dB SPL, broadband). Three speech materials were used: monosyllabic words, low-context sentences and high-context sentences. To avoid ceiling effects and upward spread of masking, all measurements were performed in stationary speech-shaped noise with the stimuli highpass-filtered at 1.4 kHz. Significant RO effects were found in the speech scores collected with the two low-context materials but not the high-context material. Overall, this suggests that low-context sentences allow for sensitive measurements of rollover effects in individual listeners.