Time-compressed speech intelligibility in different reverberant conditions

• This study shows that STI gives reliable results for different speech rates.
• There is a statistically significant difference between TCT results for various RTs.
• TCT is well correlated with RT. It decreases with an increase of RT.
• For STI > 0.5 doubling the AF does not significantly affect intelligibility.
• For lower STI values, even small acceleration is crucial for speech intelligibility.

The aim of this study was to determine how different reverberant conditions affect subjective perception of fastened speech. The objective parameters used for a description of room acoustics quality were Reverberation Time (RT) and Speech Transmission Index (STI). In relation to these parameters the Time-Compression Threshold (TCT) had been measured for normal hearing listeners younger than 30. The measuring test was based on artificially generated room impulse responses, MATLAB implementation of a phase vocoder, the Polish Matrix Test (PMT) combined with the 1-up/1-down adaptive procedure. As expected, the value of TCT decreases with an increase of RT and is highly correlated with STI. Therefore, the TCT parameter can be treated as an another sufficient estimator of acoustical quality of an enclosure in the context of speech intelligibility.