The Effect of Reverberation Time and Signal-To Ratio on Word Recognition Scores by Adults and Children in Classrooms

Abstract

This paper seeks to assess the effect of reverberation time, distribution of reverberation time over the frequency range and signal-to-noise ratio on speech intellibility by adults and children in classrooms by the use of phonetically balanced monosyllabic Turkish word recognition tests. Two sets of 25-items phonetically balanced monosyllabic Turkish words were recorded in a full anechoic chamber. Auralizations of the recordings were developed in an acoustic simulation software for a range of reverberation time of 0,8 seconds (average of 500 Hz, 1000 Hz ve 2000 Hz), 0,4 seconds (average of 500 Hz, 1000 Hz ve 2000 Hz) and 0,4 seconds (125-4000 Hz) and two signal-to-noise ratios of 0 dB and 15dB in a typical classroom. Listening tests developed from auralizations were presented to adults and children. The results show that when reverberation time (average of 500 Hz, 1000 Hz ve 2000 Hz) is reduced from 0.8 seconds to 0.4 seconds for both signal-to-noise ratios of 0 dB and 15 dB, the percentage of speech recognition scores increases in both adults and children. However, in case of 0 dB signal-to-noise, when the reverberation time falls from 0.4 seconds (average of 500 Hz, 1000 Hz ye 2000 Hz) to 0.4 seconds (125-4000 Hz) while there is no significant improvement in the word recognition scores by adults, there is a significant improvement in childrens' scores. For the 15 dB signal-to-noise ratio case, reverberation time of 0,4 seconds (125 - 4000 Hz) does not have a notable impact on word recognition scores for both children and adults.