Investigation of the Appropriate Reverberation Time in Learning Spaces for Elderly People Using Speech Intelligibility Tests

Abstract

The Republic of Korea is currently an aging society, and it will enter an ultra-aging society in 2025. This study aimed to investigate the undesignated appropriate reverberation time of learning spaces for elderly people in Korea. For this purpose, a virtual sound field was created, and the anechoic sounds were convoluted with the virtual sound field to control the reverberation time via absorption rate adjustments. Using a virtual sound field, auralized materials were made which have five different conditions with a reverberation time ranging from 0.4 s to 1.2 s. Speech intelligibility tests were conducted in both elderly and young people using headphones. Consonant–Vowel–Consonant (CVC) tests were undertaken. Preliminary experiments were performed to adjust the difficulty levels of speech intelligibility via normal young adults. The test order was nonsequential, and the sound output level was 60 dB(A). As a result, the test scores were found to decrease with an increase in the reverberation time. In addition, it was revealed that the test scores fell by 32.4% compared with the scores of normal adults under the same reverberation conditions. When the reverberation time was longer than 0.8 s, the test score was reduced by up to 13.3%; therefore, learning spaces for elderly people may require reverberation times shorter than 0.8 s. If the proposed reverberation time were applied to learning spaces for the elderly, it is believed that it could provide an appropriate sound environment for the elderly.