Effects of urgent speech and congruent/incongruent text on speech intelligibility for older adults in the presence of noise and reverberation

Abstract

Public address (PA) announcements are widely used, but noise and reverberation can render them unintelligible, and such an environment tends to degrade speech intelligibility more for older adults (OAs) than for younger adults (YAs). Furthermore, in an emergency, textual information available to the public may not coincide with PA announcements, and this mismatch may also contribute to degrading the intelligibility of the announcement. In this study, speech spoken in a normal or urgent style and preceded by congruent or incongruent text was presented to OA participants to investigate the effects of these parameters on word intelligibility in the presence of babble noise and reverberation. This study also investigated age-related differences between OAs and YAs using the same stimuli. The results showed that, while YAs performed better than OAs, the effect of urgent speech did not significantly differ with age. Urgent speech was more intelligible than normal speech, and the congruent text condition was more intelligible than the incongruent and no text conditions. An exploratory analysis showed that urgent speech improved speech intelligibility for OAs when congruent text was available, but not when absent or incongruent. Without congruent information, this listening test may have been too demanding for OAs, who could have had more difficulty processing the fixed timeline of the listening test, the faster urgent speech relative to normal speech, and informational masking because of the slowing of cognitive processing with age. A correlation was found between the average word correct rate for urgent speech and average audiometric thresholds; on the other hand, increased fundamental frequencies in urgent compared with normal speech was not the main predictor of the intelligibility of urgent speech among the OAs. The congruent text benefit in urgent speech was larger for OAs than for YAs in the previous study using the same stimuli. This demonstrates that compared with YAs, OAs may rely more on supportive prior knowledge or receive more benefit from the preceding text in challenging listening environments. These findings imply that age-related cognitive decline may explain the difficulties in speech perception in the presence of noise and reverberation among OAs; however, no definitive conclusions can be drawn. These results suggest that simple combinations of speaking style and textual information affect the intelligibility of emergency PA announcements among OAs, and thus, audiovisual congruence should be considered when announcements are made in public spaces.