Abstract
The aim of this work was to measure subjective speech intelligibility in
an enclosure with a long reverberation time and comparison of these
results with objective parameters. Impulse Responses (IRs) were first
determined with a dummy head in different measurement points of the
enclosure. The following objective parameters were calculated with Dirac
4.1 software: Reverberation Time (RT), Early Decay Time (EDT), weighted
Clarity (C50) and Speech Transmission Index (STI). For the chosen
measurement points, a convolution of the IRs with the Polish Sentence Test
(PST) and logatome tests was made. PST was presented at a background of a
babble noise and speech reception threshold - SRT (i.e. SNR yielding 50%
speech intelligibility) for those points were evaluated. A relationship of
the sentence and logatome recognition vs. STI was determined. It was found
that the final SRT data are well correlated with speech transmission index
(STI), and can be expressed by a psychometric function. The difference
between SRT determined in condition without reverberation and in
reverberation conditions appeared to be a good measure of the effect of
reverberation on speech intelligibility in a room. In addition, speech
intelligibility, with and without use of the sound amplification system
installed in the enclosure, was compared.
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