Effects of acoustic features modifications on the perception of dysarthric speech - preliminary study (pitch, intensity and duration modifications)

Marking stress is important in conveying meaning and drawing listener’s attention to specific parts of a message. Extensive research has shown that healthy speakers mark stress using three main acoustic cues; pitch, intensity, and duration. The relationship between acoustic and perception cues is vital in the development of a computer-based tool that aids the therapists in providing effective treatment to people with Dysarthria. It is, therefore, important to investigate the acoustic cues deficiency in dysarthric speech and the potential compensatory techniques needed for effective treatment. In this paper, the relationship between acoustic and perceptive cues in dysarthric speech are investigated. This is achieved by modifying stress marked sentences from 10 speakers with Ataxic dysarthria. Each speaker produced 30 sentences using the 10 Subject-Verb-Object-Adjective (SVOA) structured sentences across three stress conditions. These stress conditions are stress on the initial (S), medial (O) and final (A) target words respectively. To effectively measure the deficiencies in Dysarthria speech, the acoustic features (pitch, intensity, and duration) are modified incrementally. The paper presents the techniques involved in the modification of these acoustic features. The effects of these modifications are analysed based on steps of 25% increments in pitch, intensity and duration. For robustness and validation, 50 untrained listeners participated in the listening experiment. The results and the relationship between acoustic modifications (what is measured) and perception (what is heard) in Dysarthric speech are discussed.