[Influence of speech rate and loudness on speech intelligibility].

Background: contextual cues intrinsic to speech stimuli can have an influence on speech intelligibility measurements; however, the influence of cues that depend on the acoustic signal, such as speech rate and vocal loudness, need further investigation.

Aim: to examine whether possible reductions in the articulatory rate and increase in vocal loudness, associated to the production of different speech stimuli, can have an influence on speech intelligibility measurements.

Method: participants of this study were thirty normal speakers and sixty normal listeners. Speakers were recorded during the repetition of three lists of speech stimuli (sentences, words and pseudo words). The averages of the articulatory rate (syllables per second) and of the vocal loudness (decibel) were calculated for each speaker according to their performance in each repetition task. Speech intelligibility was measured based on the orthographic transcription of the speech samples; the score was calculated in terms of percentage of correctly transcribed words.

Results: it was observed that articulatory rates were statistically different between the three types of stimuli; however, the stimuli produced with the lowest articulatory rate (pseudo words followed by words) did not present higher speech intelligibility scores. Vocal loudness was statistically higher during the repetition of pseudo words; however, this increase did not have an influence on the speech intelligibility scores.

Conclusion: the reduction of the articulatory rate or the increase of vocal loudness did not have an influence on the speech intelligibility measurements, indicating that contextual cues have a greater impact on speech intelligibility than the independent cues given by the acoustic signal.