Comparison of Acoustic and Kinematic Approaches to Measuring Utterance-Level Speech Variability

Abstract

Purpose-The spatio-temporal index (STI) is one measure of variability. As currently implemented, kinematic data are used, requiring equipment that cannot be used with some patient groups or in scanners. An experiment is reported that addressed whether STI can be extended to an audio measure of sound pressure of the speech envelope over time, that did not need specialized equipment.Method-STI indices of variability were obtained from lip track (L-STI) and amplitude envelope (E-STI) signals. These measures were made concurrent whilst either fluent speakers or speakers who stutter repeated "Buy Bobby a puppy" 20 times.Results-L-STI and E-STI correlated significantly. STI reduced with age for both L-STI and E-STI. E-STI scores and L-STI scores discriminated successfully between fluent speakers and speakers who stutter. Conclusion-The amplitude envelope over time STI scores can be used to obtain an STI score. This STI score can be used in situations where lip movement STI scores are precluded.

Development of speech motor control: Lip movement variability

“…Variability, assessed by the STI, decreased throughout the acquisition phase. Finally, Howell et al (2009) showed a moderate but significant correlation between the STI for lip movements and the rectified and integrated audio signal for the same utterance.…”

Quantitative Assessment of Interutterance Stability: Application to Dysarthria

“…Participant numbers in previous studies have therefore been low, impacting on the statistical power and predictions made by these experiments. In order to address these problems, methods involving acoustic data collection and analysis have been successfully validated in replicating findings of the kinematic STI (Howell, Anderson, Bartrip, & Bailey, 2009). Acoustic recordings are a well established method of data collection in speech disorders and allow capturing of performance from a large number and wider variety of speakers.…”

Assessment of Childhood Apraxia of Speech: A Review/Tutorial of Objective Measurement Techniques

“…At the level of acoustic inconsistency, measures such as the acoustic spatiotemporal variability indices (e.g., envelope-based spatiotemporal index [E-STI]; Howell, Anderson, Bartrip, & Bailey, 2009) or voice onset time (VOT) variability (Iuzzini-Seigel, 2012) have clinical potential for differential diagnosis and treatment progress monitoring in CAS, but they have rarely been applied in this population. Generally, children's VOTs are more variable than adults' VOTs, and variability decreases with age and stabilizes around the age of 11 years (Auzou et al, 2000;Whiteside, Dobbin, & Henry, 2003).…”

“…Acoustic Spatiotemporal Variability Indices Assessment of speech variability via audio signals is clinically feasible even in difficult-to-test populations and has been recently proposed by several researchers (Anderson, Lowit, & Howell, 2008;Cummins, Lowit, & van Brenk, 2014;Howell et al, 2009; see Table 5). The acoustic STI is calculated in a similar manner to its kinematic variant but from the amplitude envelope derived from rectified and low-pass filtered speech audio recordings (Howell et al, 2009). As the source signal for variability calculation is the amplitude envelope, Howell et al (2009) refer to this as E-STI.…”

“…The acoustic STI is calculated in a similar manner to its kinematic variant but from the amplitude envelope derived from rectified and low-pass filtered speech audio recordings (Howell et al, 2009). As the source signal for variability calculation is the amplitude envelope, Howell et al (2009) refer to this as E-STI. The E-STI measure captures the joint spatial and temporal variation in the patterning of speech amplitude envelopes over repeated utterances.…”