The effects of F0, intensity and durational manipulations of the perception of stress in dysarthric speech

Lowit, Anja and Ijitona, Tolulope and Soraghan, John (2017) The effects of F0, intensity and durational manipulations of the perception of stress in dysarthric speech. In: 7th International Conference on Speech Motor Control, 2017-07-05 - 2017-07-08.

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Marking stress plays an important role in conveying meaning and directing the listeners attentionto the important parts of a message. Extensive research has been conducted into howhealthy speakers produce stress, with the key phonetic cues acknowledged as F0, intensity andduration (Bolinger 1961). We also know that speakers with dysarthria experience problemsin marking stress successfully (Lowit et al., 2012, Patel & Campellone, 2009). However, wecurrently lack sufficiently specific information on these deficits and potential compensatorytechniques to allow Speech and Language Therapists (SLTs) to provide effective treatmentmethods to address stress production problems.In order to build an evidence base for intervention, it is essential to first establish therelationship between features of disordered stress production and their perceptual outcomes.In particular, we need to know which phonetic cues (or combinations thereof) are most salientand what degree of change needs to be achieved in order to signal stress effectively to listeners.This project aims to explore these questions in detail by performing perceptual experimentson data from disordered speakers that have been acoustically manipulated, in order to produceguidance to clinicians on how to improve their patients ability to signal stress successfully.We used contrastive stress sentences from 10 speakers with ataxic dysarthria. Each speakerproduced 30 sentences, i.e. 10 sentences (SVOA structures) across 3 conditions (stress on initial(S), medial (O), or final (A) target words). Sentences were perceptually scored by 5 listenersregarding the location of the stress target. We then chose 15 utterances where listeners hadbeen unable to identify the target, five for each of the sentence positions. These utteranceswere subsequently manipulated acoustically by incrementally increasing the F0, intensity andduration of the target words, in accordance with the degree of change observed in the healthycontrol group. In addition, pausing patterns as well intonation contours were altered. Themanipulated utterances were played to 50 listeners to evaluate what degree and combinationof alteration resulted in correct identification of the stress target.We will report on the patterns of impairment observed in the disordered speech samples,as well as the impact of the above manipulations on listener accuracy. This will provide informationfor future studies on stress production regarding focus of analysis, as well as guideclinicians on how best to address deficits in this area in their patients.