Semantic Context Can Mask Intelligibility Declines at Above-Conversational Speech Levels in Normal-Hearing Listeners

Abstract

Purpose: While speech audibility generally improves with increasing level, declines in intelligibility are inconsistently observed at above-conversational levels, even in listeners with normal audiograms (NAs). The inconsistent findings could be due to different types of speech materials, ranging from monosyllabic words to everyday sentences, used across studies. Here, we hypothesized that semantic context can “mask” intelligibility declines at high levels by constraining plausible response options. Method: Intelligibility was assessed in speech-shaped noise with monosyllabic words, sentences without semantic context, and sentences with semantic context. Two presentation levels were used: 80 and 95 dB SPL broadband. Bandpass filtering was applied to minimize upward spread of masking. Twenty-two young adults with NAs were tested. Results: Poorer performance at the higher level was found with the monosyllabic words and context-free sentences but not with the context-rich sentences. The scores obtained at the higher level with the two context-free materials were strongly correlated. The correlation was independent of the lower-level scores, suggesting that the high-level performance declines reflect “normal” auditory functioning. Conclusions: Young adults with NAs show intelligibility decreases at above-conversational levels when tested with speech materials without semantic context. Top-down processing as facilitated by context information can mask such declines.

Amplitude Compression for Preventing Rollover at Above-Conversational Speech Levels

“…These authors argued that synaptopathy in LSR fibers may lead to a weaker middle-ear muscle reflex, which in turn can affect SI by reducing the attenuation of low-frequency input signals and thus increasing upward spread of masking. While Fereczkowski and Neher ( 2023b ) showed that RO can be found in listeners with normal audiograms when tested with highpass-filtered stimuli (i.e., under conditions of little, if any, upward spread of masking), the putative link between cochlear synaptopathy and speech perception (including RO) is likely both direct and indirect. More research is necessary to better understand its nature.…”

“…While monosyllabic words (and linear amplification) were used by Fereczkowski and Neher (2023a) , sentence-based materials were considered more suitable for evaluating the compression settings tested here. Further, since semantic context information can mask intelligibility declines at above-conversational presentation levels ( Fereczkowski & Neher, 2023b ), context-free sentences from the Danish DAT corpus ( Nielsen et al, 2014 ) were used for assessing SI in quiet. For assessing SI in noise, everyday sentences from the Danish version of the hearing-in-noise test (HINT; Nielsen & Dau, 2011 ) were used.…”

Influence of Clinical Fitting Rationales on Rollover at Above- Conversational Speech Levels

“…Also, RO presence was associated with poorer speech-in-noise performance measured 10 dB above the individual most comfortable speech level, henceforth referred to as the 'MCL+10' level. In a subsequent study, we measured SI in quiet with nonlinear amplification [4]. A subset of the listeners from our previous study with clear RO was tested.…”