The Effects of Noise and Reverberation on Listening Effort in Adults With Normal Hearing

Objectives: The purpose of this study was to investigate the effects of background noise and reverberation on listening effort. Four specific research questions were addressed related to listening effort: (A) With comparable word recognition performance across levels of reverberation, what are the effects of noise and reverberation on listening effort? (B) What is the effect of background noise when reverberation time is constant? (C) What is the effect of increasing reverberation from low to moderate when signal to noise ratio is constant? (D) What is the effect of increasing reverberation from moderate to high when signal to noise ratio is constant? Design: Eighteen young adults (mean age 24.8 years) with normal hearing participated. A dual-task paradigm was used to simultaneously assess word recognition and listening effort. The primary task was monosyllable word recognition, and the secondary task was word categorization (press a button if the word heard was judged to be a noun). Participants were tested in quiet and in background noise in three levels of reverberation (T30 < 100 ms, T30 = 475 ms, and T30 = 834 ms). Signal to noise ratios used were chosen individually for each participant and varied by reverberation to address the specific research questions. Results: As expected, word recognition performance was negatively affected by both background noise and by increases in reverberation. Furthermore, analysis of mean response times revealed that background noise increased listening effort, regardless of degree of reverberation. Conversely, reverberation did not affect listening effort, regardless of whether word recognition performance was comparable or signal to noise ratio was constant. Conclusions: The finding that reverberation did not affect listening effort, even when word recognition performance was degraded, is inconsistent with current models of listening effort. The reasons for this surprising finding are unclear and warrant further investigation. However, the results of this study are limited in generalizability to young listeners with normal hearing and to the signal to noise ratios, loudspeaker to listener distance, and reverberation times evaluated. Other populations, like children, older listeners, and listeners with hearing loss, have been previously shown to be more sensitive to reverberation. Therefore, the effects of reverberation for these vulnerable populations also warrant further investigation.