Speech rate effects on speech rhythm

This acoustic study investigates speech rhythmic restructurings due to speech rate increase in Brazilian Portuguese. Rhythmic restructuring is considered here as the reorganization of stress groups due to speech rate increase. The Dynamical Speech Rhythm model was used as a theoretical background for the acoustic analyses. Main results have shown that speech rate increase reorganizes speech rhythm and modifies some phonetic parameters in the following way: a) the standard deviation of vowel-to-vowel (VV) duration and stress group duration is smaller at faster rates; b) stress group duration tends to be constant with speech rate increase (rhythmic restructurings make VV units smaller, but with a greater number of VV units per stress group, what results in a statistically constant stress group duration); c) the number of VV units per stress group proportionally increases with speech rate increase due to rhythmic restruturings; and d) speech rate increase exacerbates the mixture character of Brazilian Portuguese rhythm, i.e., tendencies to syllable as to stress-timed rhythm.