Measuring speaking rate: how do objective measurements correlate with audio-perceptual ratings?

Objective: Although speaking rate is central for many speech disorders, no consensus exists regarding the measurement of this feature. The purpose of this study was to examine the correlations between perceptual listener evaluations and various measures of speaking rate. Furthermore, the study investigated the relationship between speaking rate and articulation rate and how pauses in speech affect the perceived tempo.

Method: Nine healthy females were selected to produce stimuli representing three habitual speech tempi during semi-spontaneous speech: slow (n = 3), neutral (n = 3) and fast (n = 3). Speaking rate was analyzed both by manual calculation and through automatic detection by a script to the computer-based program Praat. Thirty untrained male and female listeners evaluated the recordings with regard to speech tempo on visual analogue scales from very slow to very fast.

Results: Large, significant correlations (Pearson's r) were found between all objective measures of speaking rate and perceptual listener evaluations. Words/minute showed the largest correlation (.91), followed by syllables/second (.89), while articulation rate (pauses excluded) as automatically measured by the script, showed the smallest correlation (.69). Possible explanations for the findings are discussed.

Conclusion: Untrained listeners' evaluation of speech tempo in normal subjects correlated strongly with objective measurements. The results both support the use of auditive-perceptual evaluation of tempo and the use of automatic script analysis for clinical use. Speaking rate (pauses included) showed better consistency with perceptual listener evaluations than articulation rate.