## 4 Discussion
### Listener Ratings of Strain and Effort  
Twenty normal hearing listeners rated speech samples from 23 AdSD talkers on a scale of 1-100 for two auditory-perceptual dimensions: vocal strain and listening effort. Reliability analyses of the rating data revealed: (a) moderate to strong intra-rater reliability, with test-retest ratings correlations ranging from 0.56 to 0.96 for strain and 0.58 to 0.97 for listening effort and (b) excellent interrater reliability, with Cronbach's \(\alpha\) of 0.98 and 0.97 for strain and listening effort, respectively. These reliability results are consistent with previous studies by [PERSON] and [PERSON] [14,16] investigating the relationship between voice quality attributes and listening effort, albeit with a different voice disorder population (i.e., tracheoesophageal and electrolarynx voices, respectively).  
Figure 5: (a) Peak pupil dilation (PPD) values extracted from averaged pupil tracks associated with each talker stimulus. Talker samples that resulted in the two highest and lowest PPD values associated are highlighted in purple and red colours, respectively. (b) Scatter plot between the averaged perceptual ratings of strain and the PPD values extracted from averaged pupil tracks, along with the linear regression fit to the data. (c) Scatter plot of PPD values extracted from average pupil tracks with the averaged perceptual ratings of listening effort, along with the linear regression fit to the data.  
Data from auditory-perceptual evaluation of samples revealed that the talkers exhibited various degrees of vocal strain. For example, some of the speech stimuli were rated as less strained (e.g., Talkers 4, 8, 10, and 15) compared to others who were consistently judged as exhibiting increased levels of strain (e.g., Talkers 1, 2, 9, 18, and 21). More importantly, the auditory-perceptual data demonstrated that the higher the ratings for strain, the more listening effort was expended. For instance, Talkers 8 and 10 were rated the lowest in terms of strain and were also judged to require the lowest degree of listening effort; in contrast, Talkers 1 and 18 were judged as the most strained and were evaluated as requiring the most listening effort. Across the 23 speech stimuli, the averaged vocal strain and listening effort ratings exhibited a significantly high positive correlation (r = 0.90). To the best of our knowledge, no study to date has evaluated perceived listening effort in the context of talkers with AdSD and our results confirm increased listening effort is required as AdSD severity increases. Furthermore, given that the speech stimuli used in this study were highly intelligible, these results are consistent with previous findings suggesting that the challenges faced by listeners are beyond those related to audibility [13] or intelligibility [21]. Such perceptual challenges increase when more cognitive effort is expended to channel attention and concentration in order to achieve a listening goal. This is particularly important when the quality of an auditory signal is distanced from optimal [13], as is the case with speech samples from talkers with greater AdSD severity.  
As shown in Figure 2a, out of the 23 AdSD talkers evaluated, 21 were judged to have a higher strain rating relative to the listening effort, a finding that was not unexpected. Interestingly, results revealed that listeners rated stimuli from Talkers 5 and 20 to have higher ratings for listening effort relative to the strain ratings (see Figure 2b). Investigations into the speech samples from these talkers divulged that their voices are more characterized by increased breathiness, rather than strain. Thus, the auditory-perceptual ratings for these two Talkers (5 and 20) confirm that listeners were in fact attending to the rating task, and rated the listening effort dimension holistically. These stimuli were not perceived to be highly strained but they still deviated from normal, which subsequently required increased listening effort.