## 1 Introduction
### Listening Effort  
The success of communication depends on both the talker and listener [5]. Receptive or expressive impairments will alter the balance of responsibilities in any communication dyad. According to [PERSON] and [PERSON] [9], processing demands in a listening situation depend on the interaction between the degradation or distortion in the utterance and listeners' own cognitive resource capacity. Therefore, as speech or voice deviates from normal expectation, increasing demand is placed on the listener which may subsequently require additional levels of cognitive processing. Communication success with dysphonic talkers may, therefore, be hampered as listeners may not wish to carry the enhanced load of processing and responding to such disordered speech [10; 11]. This increased processing load on the listener has been defined with a variety of terms such as cognitive effort or cognitive load, effortful listening, listening effort, resourceful listening, and/or listening difficulty [9; 12; 13; 14], with the term _listening effort_ used in this paper.  
Listening effort can be evaluated subjectively through ratings and self-report questionnaires and objectively through physiological measures [13]. Substantial literature exists on behavioural assessment of listening effort with degraded speech samples, challenging listening environments, and/or listener-specific factors (e.g., hearing loss) [9; 13; 15]. However, only a few studies have investigated the behavioral assessment of the effort required when listening to dysphonic speech samples. For example, [PERSON] and [PERSON] [14] obtained ratings of acceptability and listening effort from naive listeners for tracheeosophageal speech samples. They reported a high degree of inter-rater reliability in listener effort ratings, and a very strong correlation between acceptability and listening effort ratings. In a subsequent study, [PERSON] and [PERSON] [16] collected intelligibility, acceptability, and listening effort ratings from naive listeners for electrolarynx speech samples. Similar to their earlier study, strong correlations were found between intelligibility and listening effort ratings, as well as between acceptability and listening effort ratings. More interestingly, there was greater variability in listening effort ratings for speech samples with 50% or more intelligibility rating, indicating that some speech samples demand greater listening effort even though they are intelligible. To the best our knowledge, no studies have investigated the subjective evaluation of listening effort with AdSD speech samples.  
For physiological assessment of listening effort, [PERSON] et al. [13] identify two main categories. The first involves measures of brain activity such as magnetoencephalography (MEG), evoked-response potentials (ERPs), alpha power in electroencephalography (EEG), and functional magnetic resonance imaging (fMRI). These types of measures provide information regarding the timing and precise localization of cortical activity in response to stimuli. The second category of physiological measures for assessing listening effort includes those that quantify responses of the autonomic nervous system which involves both sympathetic and parasympathetic responses. For example, changes in pupil size, hormonal changes, skin conductance, and cardiac responses can be used as indices of one's autonomic response [13]. This paper focuses on pupil dilation when listening to speech samples produced by AdSD talkers.