gms | German Medical Science

Pupil size varies as a function of autonomic nervous system activity and can be used to quantify listening effort. Since differences between optimal and near optimal listening conditions are often not reflected by speech intelligibility, pupil size can indicate differences in listening effort that can be attributed to experimental manipulations such as changes in hearing aid programs [1]. While pupillometry has been widely used at negative signal-to-noise ratios (SNR), everyday listening situations often involve positive SNRs [2]. For instance, speech recognition can be challenging in reverberant listening environments, in particular at faster speaking rates [3].

In the current study, we investigated the effect of fast and slow speaking rates on pupil dilation in different reverberant environments. Thirteen hearing-impaired participants took part in the study under aided listening conditions. Speaking rate was increased artificially by time-compressing signals using overlap-add techniques. Room acoustics with low and high levels of reverberation were simulated using Higher Order Ambisonics. In addition, a hearing aid program for speech in quiet was compared to a program with dereverberation.

Results showed that despite ceiling intelligibility at slow and fast speaking rates, pupil dilation was larger for fast speech when reverberation was low, indicating increased listening effort. While more reverberation was associated with larger pupil dilation, speech intelligibility was lower. Dereverberation did not benefit speech intelligibility or listening effort. Findings support the potential use of pupil dilation as a measure of listening effort at optimal intelligibility levels.