Dysarthrias are motor speech disorders typically associated with problems with the strength, speed, range, steadiness, tone or accuracy of the musculature used to produce speech, that result from damage of the central or peripheral nervous system (Duffy, 2013). Dysarthrias may compromise only a single component of the vocal tract, or may have a global effect on the speech production systems and affect multiple aspects of spoken language. Usually the effects of dysarthria are global rather than focal (Kent, 2000). In any case, the resulting speech disorder can compromise to a lesser or greater extend the individual’s ability to communicate and participate socially, and it is usually responsive to behavioral intervention.

This study examines the acoustic and perceptual effects of Greek dysarthria on lexical stress via an in-depth investigation of three speaker with dysarthrias. Additional phonetic characteristics of dysarthric speech are analyzed, including voice quality and consonant and vowel characteristics. Data from a number of different speaking tasks are used, including isolated word production, vowel prolongation and syllable repetition.

The purpose of this study is to investigate the effects of dysarthria on speech characteristics in Greek with particular emphasis on the signaling of lexical stress, through perceptual and acoustic analyses. Apart from the realization of lexical stress, other possibly deviant speech characteristics were examined, including voice quality, consonant production and vowel production. A case study approach was used; data were collected from three Greek individuals with dysarthria and normal speakers that served as controls. The data primarily included isolated word production as well as vowel prolongation and syllable repetition tasks. The single word data were used for the acoustic analysis of lexical stress and for the stress identification task, both of which are described in detail in the following sections. Connected speech recordings, including sentence repetition and passage reading were also made as part of the initial assessment of the overall perceptual speech characteristics of the participants with dysarthria.

The main acoustic cues of lexical stress in Greek, i.e. duration and intensity, were analyzed in all three speakers with dysarthria. Additionally, the use of fundamental frequency as a cue for stress was assessed in Anna, the effects of phonation patterns on the acoustic prominence relations of stressed and unstressed syllables were assessed in Chris and the role of vowel quality in stress signaling was assessed in Maria.

This chapter presents in detail the results of the additional acoustic analyses for each case study. The acoustic characteristics of voice and vowel quality were analyzed in all three participants with dysarthrias, whereas the realization of stop consonants was acoustically assessed only in Chris and Maria.

This chapter summarizes and discusses the overall results of this study. To that end, it will be shown how the findings answered each of the study questions and contributed to the understanding of the acoustic and perceptual effects of dysarthria in Greek. Next, the implications of this study will be discussed, focusing on the clinical application of the research findings in the assessment and therapy of dysarthria and on the importance of cross-language research in motor speech disorders. Finally, possibilities for future research will be explored.

Recent research on how individuals with Parkinson’s disease (hereafter PD) perceive that their communication has changed since onset of the disease reveals that most of these individuals feel a negative impact, one that includes fear of social interaction and withdrawal. As one participant in another study stated, “[Sometimes] I just can’t do the conversation, I just say, oh, I hope they don’t talk to us, you know, they’ll just say, hello, how are you, and walk away” (Miller, Noble, Jones, & Burn, 2006). The striking thing about the individuals in these studies is that these perceived changes and their impact on communication could occur before any apparent decline in intelligibility or referral to speech-language pathologists (Miller et al., 2006; Miller, Noble, Jones, Allcock, & Burn, 2008). One possible metric for this perceived communicative change for the worse in those with PD and their caretakers is speech naturalness (Martin, Haroldson, & Triden, 1984), a standard of measurement commonly used by speech-language pathologists and the subject of much research attempting to define its properties.

Experiment 1 focused on looking at the prosodic characteristics of subjects’ speech at varying levels of linguistic complexity. The methods used for data collection and analysis are described in detail below, followed by the results.

Experiment 2 focused on obtaining naturalness judgments for a portion of the speech samples collected in Experiment 1. The methods used for data collection, judging, and analysis are described in detail below, followed by the results.

This chapter endeavors to analyze the results of the two experiments together in order to address the final aim of this study: to describe the prosodic and acoustic characteristics of dysarthric speech that is rated either highly natural or unnatural. In order to address this goal, speech samples were first ranked most and least natural for each speaker, then the acoustic correlates of prosody of each of these samples were investigated. In order to rank which speech samples were rated most and least natural overall for each speaker, naturalness ratings from all reliable judges were first averaged for each sample. Then the averaged naturalness ratings per sample were ranked from lowest to highest for each subject. The acoustic characteristics of the top and bottom third of all ranked samples for each subject, the most and least natural overall rated samples respectively, will be discussed shortly.

This chapter will summarize and discuss the overall results of this study. It will start out by reviewing the research questions posed at the end of Chapter 7, then will address how the results answered each question and furthered our understanding of the prosodic characteristics of PD and how they relate to speech naturalness. Next the implications of this study for how the concept of speech naturalness is defined and used in the field of speech-language pathology will be discussed. This chapter will then discuss the limitation of the study, including the sample size and population, as well as the methods used. Finally, suggestions for future research considering the results presented here will be explored.

In the chapters that follow we shift our attention to dysarthria secondary to Multiple Sclerosis (MS). We also see a change in methodological approach. The two studies discussed in the book so far have taken a primarily experimental approach to the study of dysarthria. The study described in the proceeding chapters differs in that the methodology adopted is qualitative and the focus is on naturally occurring, conversational speech. This study adopts the approach of interactional phonetics to investigate the manifestation of dysarthria secondary to MS in the conversational speech of two adults from Louisiana, USA. Specifically, we explore how difficulties associated with a breakdown in understanding arise in conversation and how these difficulties are subsequently managed. Crucially, due to the method adopted, these breakdowns in understanding were not elicited or scripted but instead arose naturally during the conversations we recorded. The phonetic and linguistic features of each breakdown are considered, and the subsequent conversational turns are analyzed under a framework inspired in part by conversation analysis (Schegloff, 2002). This chapter serves as an introduction to the study, outlining the features of dysarthria secondary to MS (12.2), the assumptions of interactional phonetics as a method of inquiry (12.4), and then the main research aims of the study (12.5).

In the preceding chapter we have shown that existing studies looking at the phonetics of dysarthria secondary to MS have focused largely on read words, read sentences and some elicited connected speech. In this study our focus lies instead on the manifestation of MS dysarthria in conversational speech, and in particular the social action we call repair. In this chapter we introduce the concept of repair in more detail as a phenomenon of naturally occurring conversation. We will show that repair is both common yet structurally complex. We outline a typology of repair and focus particularly on the concept of self-repair; the conversational act of addressing a problem with the understandability or intelligibility of some preceding talk. In section 13.4 we focus on repair in conversations where one or more participant has a communication difficulty, particularly in relation to intelligibility. Finally, we summarize what is known about the phonetics of repair, focusing mostly on conversations where the participants do not have a communication difficulty.

In this chapter we outline the methodology adopted during the study. The method differs in a number of ways from the methods used in the first two studies. Most notably, the speech samples came from naturally occurring conversation. Moreover, a data driven, qualitative approach to analysis was taken. This can be contrasted with a more traditional, experimental approach. The purpose of this study was to investigate the acoustic-phonetic features associated with self-repair in the conversational speech of two persons with dysarthria secondary to MS. Further to this, to explore the techniques adopted by the conversational participants to resolve difficulties with understandability and as such participate in the ongoing repair sequences. The methodology was guided by interactional phonetics and as such the data were recordings of naturally occurring conversational speech. These were transcribed using conventions inspired primarily by conversation analysis. Turn-by-turn interactional and phonetic analysis was then used to uncover the manifestation of dysarthria in conversation. In this chapter we describe the participants, both of whom where adults with a diagnosis of MS, and their speech characteristics. We also outline the data collection technique and the phonetic analysis. The latter part of the chapter will be useful for any readers wanting to carry out their own interactional phonetic studies, particularly focusing on communication difficulties.

In this chapter we outline the results of our interactional phonetic study. In section 15.2 we introduce the acoustic properties that we found to be common to the interruption point and interregnum of repair sequences. We also discuss the extent to which certain acoustic parameters seem to be used to signal these phases of conversational speech. We then move on to discuss modification repairs in section 15.3, with particular attention being given to those repairs that can be classed as ‘intelligibility repairs’. These repairs will be discussed according to the acoustic features identified in chapter 14; specifically: intensity, duration, frequency, and other articulatory properties of the signal. Acoustic analyses will be supplemented with impressionistic phonetic transcriptions carried out using the IPA where necessary. The extracts are discussed using a system of single case analysis. This is to facilitate consideration of social-interactional information when making claims about the phonetic design of turns in talk.

The aim of the study reported in this section of the book was to look at the manifestation of dysarthria secondary to MS in naturally occurring conversational speech. More specifically, to look at the acoustic-phonetic characteristics of repair sequences; those occurrences in natural conversation associated with misunderstanding. It is hoped that the results provide information about the modifications made by dysarthric speakers in order to enhance their speech intelligibility and inform theories of speech motor control in normal and disordered populations. The methodology adopted was interactional phonetics. This was in order to facilitate the analysis of repair in spontaneous, conversational speech. It is here, we have suggested, that the symptoms of speech disorders like dysarthria are most likely to present (Leuschel & Docherty, 1996; Rosen, Kent, Delaney, & Duffy, 2006; Tjaden & Walting, 2003). Interactional phonetics is more commonly used for the analysis of conversations without the involvement of communication difficulties (see Couper-Kuhlen, 2007; Couper-Kuhlen & Ford, 2004; Curl, 2004; Local, 1992; Ogden, 2001) but with some history of applications to disordered speech production (Auer & Rönfeldt, 2004; Local and Wootton, 1995; Tarplee & Barrow, 1999). It is an approach that encourages the use of spontaneous conversation as a data source. It also recognizes the role of very fine phonetic detail in conveying meaning in conversation. In carrying out the joint analysis of the sequential organization of talk and the phonetic design of participant contributions, the consequences of acoustic variation to interaction can be discovered. In this chapter we summarize these results, discuss the implications of the work, and reflect on the use of interactional phonetics.

Dysarthria is a motor speech disorder caused by neurological injury. Compromised or impaired motor control – whether due to muscle weakness, paralysis, paresis, or lack of coordination – of one or more of the speech subsystems results in speech difficulties. The symptoms and characteristics of the various dysarthrias vary widely by classification and even between individuals with the same type of dysarthria. The studies presented here show the myriad of ways speech can be affected by dysarthria and possibilities for looking at and analyzing a speech disorder that is so varied in its presentation in a way that both captures the complexity and most pertinent features in a clinically useful manner. In the remainder of this chapter we will present summaries of the three investigations described in this book. From there we will consider the broader implications of these studies on work in dysarthria and in phonetics and the interaction between these two fields. We conclude with a look towards future directions in clinical phonetics and dysarthria research.