Audiology and Speech Pathology - Theses
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ItemA qualitative longitudinal study exploring adjustment experiences post laryngectomy( 2021)Background: A total laryngectomy operation involves the surgical removal of the larynx for management of advanced laryngeal or hypopharyngeal cancer. A total laryngectomy nearly always has a profound impact on a person’s life. There are significant physical and functional changes as well as psycho-social consequences to adapt to post-operatively. There is currently a paucity of qualitative longitudinal laryngectomy studies exploring the phenomenon of lived experiences in the first six months post laryngectomy. Aim: To investigate the adjustment experiences of people in the first six months post laryngectomy. Methods: A qualitative longitudinal study was conducted. Participants planned for a total laryngectomy during August, 2018 – April, 2020 were recruited to the study. Each participant completed a distress screening using the Distress Thermometer and in-depth semi-structured interviews at two weeks post discharge, and at three months and six months post operation. Inductive Thematic Analysis method was chosen following the six phases described by Braun & Clarke, 2014, to analyse the data. Results: Of the six participants in the study, 14 distress screenings and in-depth semi-structured interviews were conducted and analysed (complete data sets were obtained for four participants). Distress levels were high in the pre and immediate post-operative weeks but little or no distress were reported in the longer term. Three phases of adjustment were identified; Phase one – Not normal life; Phase two – Never going to be the same again; and Phase three – Just get on with it. Clinical implications of results: The insights from this study can lead to improved clinical practice regarding assisting people in the early phases of adjustment. Targeted education, supportive care and independence care training are essential and positively impacts adjustment.
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ItemMotor speech phenotype of Huntington’s disease: A potential clinical marker in the premanifest phase( 2021)Huntington’s disease (HD) is an inherited neurodegenerative condition caused by a mutation in the HTT gene coding for the protein Huntingtin. The autosomal dominant inheritance nature of HD makes it amenable to diagnostic and predictive genetic testing. HD is characterised by movement disorder, cognitive and psychiatric symptoms. A formal diagnosis of manifest HD is indicated by the phenotypic appearance of unequivocal movement disorder in carriers of expanded HTT gene. Prior to diagnosis of manifest HD, carriers of the expanded HD gene may show subtle changes in their fine motor skills, cognition, behaviour, and speech. The premanifest phase of HD (PreHD) may be an optimal time for introduction of disease-modifying drug trials, based on an assumption that the brain is most receptive to therapeutic changes in that period. Various intervention methods are in development, but one of the challenges in clinical trials, however, is the lack of easily accessible, sensitive and measurable biomarkers to improve onset detection accuracy, provide routine monitoring of disease progression, and evaluate intervention efficacy. The thesis explored the use of acoustic speech as a potential biomarker of HD, by (i) identifying speech symptoms in the premanifest and manifest phases of HD, (ii) examining speech stimuli and digital speech metrics that are sensitive in detecting speech changes in people carrying the expanded HD gene, and (iii) evaluating the reliability and speech metrics of speech across multiple assessment intervals. Speech was analysed perceptually and objectively, and measures of articulatory agility, voice quality, and prosody (speech-timing) were extracted and compared between people with premanifest HD, manifest HD and healthy controls. Speech outcomes were correlated to other clinical measures of motor function, fine motor performance, cognitive abilities and disease burden. A 6-month longitudinal speech investigation was also conducted to evaluate the reliability and stability of speech in PreHD. Findings from experimental studies in the thesis indicated speech differences between PreHD and control groups were audible to expert listeners (i.e., speech pathologists) using perceptual assessment of speech (Chapter 4). Objective acoustic analysis revealed speech differences on measures of articulatory agility and speech-timing between PreHD and healthy controls, but these differences are only observed in speech tasks that required a higher level of cognitive load and motor effort (Chapter 5). Speech tasks and speech metrics shown to be sensitive, reliable, and stable in PreHD and healthy controls were identified in the final chapter of this thesis (Chapter 6). Overall, these studies have explored the potential for acoustic speech measures to be utilised in clinical settings as behavioural markers of disease. The validation of speech as markers requires further research in the field, however, the thesis has provided some data on using speech to monitor disease progression and evaluate treatment efficacy in premanifest and manifest HD.
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ItemAn Assessment of Eating Behaviour and Swallow Function in People Diagnosed with Frontotemporal Dementia( 2022)Eating-related changes occur in many different types of neurological disorders but are especially prevalent in frontotemporal dementia (FTD). FTD is an umbrella term for three clinical syndromes with shared pathological features and frontotemporal atrophy on brain imaging. The variants of FTD include a cognitive-behavioural syndrome, known as behavioural variant FTD (bvFTD), and two language syndromes, semantic dementia (SD) and progressive non-fluent aphasia (PNFA). Changes to the eating process can include aberrant eating behaviours, altered diet preference and swallowing difficulties. Eating-related impairments are reported to occur in all variants of FTD, but the type, frequency and severity of the symptoms likely differ between clinical syndromes. An improved objective description of changes in eating is needed to guide appropriate management and treatment development. The aims of this research were to provide a comprehensive characterisation of the incidence rate and severity of deficits which affect the eating process, including the impact aberrant eating behaviours have on carer distress. The hypotheses of the thesis were that specific aberrant behaviours would hinder swallow safety, aberrant behaviours would decline with disease duration due to apathy and an impaired perception of food pleasantness would be associated with altered diet preferences. Fifty individuals with FTD (bvFTD n = 24; SD n =14, PNFA n = 12) underwent a comprehensive mealtime assessment battery examining clinical swallow function, aberrant eating behaviours and perceived pleasantness of food-related odours. Comparator groups included people with progressive supranuclear palsy, Alzheimer’s dementia and healthy controls. Participants were assessed at home during a single 90-minute session. A speech pathologist specialising in dysphagia and aberrant eating behaviours conducted a clinical swallow exam while the carer completed questionnaires. Carer questionnaires included the Appetite and Eating Habits Questionnaire (APEHQ) and the Neuropsychiatric Inventory Questionnaire (NPI-Q). The Clinical Assessment of Dysphagia in Neurodegeneration (CADN) was used to assess swallow function. Two novel screening tools comprised a mealtime observation and an assessment of food-related olfactory judgements. The observation was conducted over a full meal and screened for behaviours predicted to correlate to carer report of post-prandial coughing. The olfactory assessment was completed after the meal and required participants to judge the pleasantness, edibility and identification of olfactory stimuli. Collected data was reported across sub-studies. Aberrant eating behaviours were found in all FTD syndromes. Eating-related carer burden was positively associated with hyperphagic behaviours, such as overfilling the mouth, overeating and poor table manners. An abnormal eating speed and/or overfilling the mouth may exacerbate mild dysphagia symptoms and lead to mealtime coughing and choking. The occurrence, frequency and severity of eating-related symptoms otherwise varied between the syndrome groups. Impaired swallow function occurred prevalently in the PNFA cohort and in more than half of individuals with bvFTD. The bvFTD and SD group had difficulty associating a target item’s odour with its visual appearance. Eating-related changes can impede safety and increase carer distress. Most management tools are not specific to the FTD population and do not incorporate multiple domains of the eating process. Current findings will provide the base from which treatment and symptom management protocols can begin to be developed.
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ItemPatient and carer perceptions of involvement in healthcare decision making in motor neurone disease: a longitudinal study exploring the impact of communication and cognition( 2022)Motor neurone disease (MND) is a neurodegenerative disease with insidious onset resulting in progressive difficulties walking, talking, swallowing, and breathing. Decision making in MND is complex due to rapid and variable disease progression. Care focuses on symptom management and quality of life. Decision making is challenged by the need for people living with MND (plwMND) and carers to make anticipatory decisions related to interventions for symptom management. Despite the high incidence of communication impairment, there is limited literature reporting the impact on involvement in healthcare decisions. Longitudinal qualitative methods were used to explore the perceptions of plwMND and carers on their involvement in healthcare decisions. Interviews were conducted over 26 months and transcripts were analysed using inductive and/or deductive thematic analysis. Results identified participants perceived the decision-making process as aligned to ‘accepting a recommendation’ due to lack of treatment choices and disease progression necessitating interventions. Communication impairments created unique challenges for plwMND and carers due to the effort required to talk and/or use alternative communication methods. The support carers and HCPs made were essential to maximising healthcare access. Findings illustrate that information needs are individual and influenced by perceived relevancy and emotional readiness. Strategies are provided which may assist plwMND and carers to be more explicit regarding their needs and may empower them to be more involved in healthcare. Enhancements to an MND decision-making model are provided to ensure the needs of plwMND and carers are addressed and embedded in decision-making.
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ItemStudent engagement of children who are deaf or hard of hearing attending mainstream schools( 2021)Student engagement in classroom learning is recognized as being important for a child’s school success. It is a major focus in the education literature, with a range of intervention programs being designed to increase engagement levels in the classroom as a way of increasing school completion rates, and improving school outcomes for the student. Students who are deaf or hard of hearing (DHH) and attend mainstream schools may experience additional difficulties engaging in their learning compared to their peers with typical hearing. Despite this, research investigating the student engagement of children who are DHH remains sparse. To address this gap, the overarching aim of this thesis was to explore the student engagement of DHH students attending mainstream schools. This thesis consisted of two studies. The first study compared the observed and the self-reported engagement of 16 DHH students (aged 9 – 12 years) who attended mainstream schools to that of matched controls with typical hearing. Observed engagement was measured through observations in the classroom setting using the Mainstream Version of the Code for Instructional Structure and Student Academic Reponses (study 1a), and self-reports of engagement were obtained using the Classroom Participation Questionnaire (study 1b). The main finding of this study was that there were no significant differences for either observed or self-reported engagement for the group of DHH students compared to that for the group of matched controls. When looking at individual results, three individual DHH participants had lower levels of observed engagement compared to their matched control. Adverse noise levels for one student, and low vocabulary scores for another student are possible causes for these poor results. The second study was a qualitative study that used individual interviews to explore the self-perceived barriers and facilitators to engagement for DHH students attending mainstream schools. Interviews consisted of a series of question and a card-sorting activity. The same 16 DHH students who participated in study 1, participated in study 2. Thematic analysis of the interview transcripts resulted in the generation of four themes. These were: challenges to engagement, student strategies, supports to students, and teacher actions. These themes demonstrate the complex range of factors that contribute to or impede engagement of students who are DHH in mainstream classrooms.T he work undertaken for this research demonstrated that, for the participating students, there were no differences between the groups on either observed or self-reported engagement. One notable characteristic which is likely to have contributed to this positive finding was that all but one of the participants attended a mainstream school with a deaf facility. As such, it is possible that factors related to this school setting, such as having high levels of support available and having a DHH peer group within the school, may have contributed to the positive finding. Although there were no differences in engagement levels between groups, three individual DHH participants had lower levels of observed engagement compared to their matched controls. As such, some DHH students may benefit from receiving support with a specific focus on engagement. The factors identified in the second study may be used to inform professionals about the engagement of students who are DHH attending mainstream schools, and provide strategies towards reducing the barriers and increasing the facilitators to engagement for these students.
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ItemFitting and evaluating binaural hearing in adults using electric and acoustic stimulation( 2021)Abstract Background. Advances in the design of the cochlear implant electrode arrays and improved surgical techniques have resulted in the successful preservation of residual hearing after implantation. The preservation of residual hearing following cochlear implantation provides the capacity for combining electrical and acoustic stimulation in the same ear to benefit the listener. The effectiveness of electric and acoustic stimulation in the implanted ear as compared with electrical and acoustic stimulation alone has been consistently demonstrated in the research literature. There is also accumulating research evidence that supports the provision of acoustic stimulation for residual hearing in the implanted ear together with the non-implanted ear of recipients of a unilateral cochlear implant. A variety of approaches have been used in research studies to fit devices that provide electric and acoustic stimulation in either the implanted ear or in opposite ears, however, there is no comprehensive study evaluating binaural fitting strategies in adult cochlear implant users with residual hearing in both ears. Investigation of a fitting procedure that could maximise hearing outcomes for adult recipients who use electric and acoustic stimulation in the implanted ear and acoustic stimulation in the non-implanted ear would be of benefit. Objective. The overarching goal of this thesis is to examine the fitting of devices that combine electric and acoustic stimulation for cochlear implant recipients with residual hearing in both ears. Aims 1. To systematically investigate how to adjust the hearing aid acoustic output in both ears, for adults who use electric and acoustic stimulation in the implanted ear together with acoustic stimulation in the non-implanted ear. 2. To investigate the effect of varying cross-over frequency settings for electric and acoustic stimulation in the implanted ear combined with acoustic stimulation in the non-implanted ear on speech perception in noise, localisation, functional performance in real life, and music perception. 3. To investigate the relationship between the measured cochlear dead region edge frequency in the implanted ear and the selection of the preferred cross-over frequency setting in devices that provide electric and acoustic stimulation. Methods Research design. A repeated-measures, within-subject research design, in which each participant acted as their own control was used. Participants. Eleven adults with bilateral sensorineural hearing loss, who had residual hearing in both ears, and who used a unilateral cochlear implant in one ear, and a hearing aid in the contralateral ear, participated in the study. Data collection and analysis. The thesis was structured in two distinct studies. Study 1. Participants were fitted with new hearing aids in both ears. A two-staged, systematic fine-tuning procedure was used to evaluate the hearing aid output requirements for the group of eleven adults who use a Nucleus cochlear implant system in one ear together with acoustic stimulation in both ears. Firstly, a paired comparisons technique was used to determine the participant’s preferred hearing aid gain for speech intelligibility in the implanted and the non-implanted ear. Secondly, the HA was systematically adjusted to determine the hearing aid gain requirements to achieve equal loudness between electric and acoustic stimulation in the implanted ear and then for equal loudness between ears. Study 2. Performance was compared with three different cross-over frequency settings set according to audiometric criteria, following a four-week period of familiarisation with each setting. Speech perception in noise, localisation, functional performance in real life, and music perception were evaluated. On completion of all trials, participants selected their preferred cross-over frequency setting. The cochlear dead region edge frequency values were then determined for each participant using a fast-psychophysical tuning curves test. Results. Study 1. On average, participants’ preferred hearing aid gain settings were within 5 dB of the NAL-NL2 fitting formula’s prescribed gain in the implanted ear and non-implanted ear. In addition, the hearing aid gain to achieve equal loudness between electric and acoustic stimulation was higher on average than participants’ preferred loudness in the implanted ear. However, for the non-implanted ear, there was no significant difference between the gain preferred by participants and the gain required to achieve equal loudness between ears on average. Study 2. On average, cross-over frequency settings did not have a significant effect on performance scores. However, higher ratings on device usage were associated with the preferred cross-over frequency settings. All adults for whom a dead region edge frequency value could be determined using the fast-psychophysical tuning curves test preferred electric stimulation in their chosen cross-over frequency setting to start after the cochlear dead region edge frequency value in the implanted ear. Conclusions Study 1. The findings of this research suggest that the NAL-NL2 prescription provides an appropriate starting point for fitting hearing aids in adults who use a cochlear implant system in one ear together with acoustic stimulation in both ears. Secondly, the study findings suggest that there may be no benefit to performing a loudness balancing procedure between electric and acoustic stimulation in the implanted ear or non-implanted ear in a clinical setting. Using an empirically validated hearing aid prescription and real-ear measurements to verify that target gains are matched as closely as possible may be an important first step when clinically fitting electric and acoustic stimulation. Study 2. Changes in cross-over frequency settings, set according to audiometric criteria, did not affect performance. Identification of the cochlear dead region edge frequency value may potentially be helpful in determining the cross-over frequency setting for the implanted ear in routine clinical settings. Selecting a cross-over frequency setting where electric stimulation begins after the individually measured cochlear dead region edge frequency value in the implanted ear could provide an individualised approach to best fitting practices for devices that provide electric and acoustic stimulation. The findings should be interpreted with caution due to the limited number of participants in the current study. There is published literature on the potential benefit from avoiding the amplification of frequencies that incorporate cochlear dead regions for listeners with severe-profound steeply-sloping. This is the first direct examination of the relationship between the cochlear dead region edge frequency value in the implanted ear and the preferred cross-over frequency setting in adults who use electric and acoustic stimulation. Further investigation into the implications of this finding in fitting electric and acoustic stimulation is warranted. The evidence base created by this research may contribute to the development of guidelines and recommendations for clinical fitting of devices that provide electric and acoustic stimulation and may potentially lead to individualised treatment for optimal benefits in recipients of a cochlear implant with residual hearing in both ears.
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ItemThe relationship between disease status and acoustic analysis of speech in Multiple Sclerosis( 2021)Multiple Sclerosis (MS) is a common cause of disability in young adults. Modern MS treatment has markedly improved long-term outcomes for the most common type of MS, i.e., relapsing-remitting MS. However, optimal pharmacological treatment decisions depend on early detection of disease progression. Validated assessment of progression includes disability scales and standard structural magnetic resonance imaging (MRI) of the brain (brain volume changes), but these are not sensitive to the early disability worsening. More dynamic tools are required to increase the responsiveness of MS monitoring. Objective speech analysis offers several potential advantages for disease monitoring, including short assessment time, low patient effort, automation, remote assessment (via smartphone or mobile device), improved reliability via elimination of inter and intra-rater variability, and wide disability-wise suitability as speech continues to be produced even by severely disabled patients. The general aims of this thesis were to (1) review and identify gaps in the literature regarding the validity of speech to monitor MS progression, (2) examine the relationship between acoustic metrics and general neurological status or cerebellar impairment in people with MS (pwMS), and (3) describe differences in health-related acoustic metrics between mobile devices' recordings and professional-grade microphones, both of which are commonly used in research settings. Most previous studies described only differences between pwMS and healthy controls for a narrow set of acoustic speech features, with almost nonexistent information on disability or neuroimaging correlates of speech impairment in MS. In the current study, we observed a moderate strength relationship between speech acoustic features and general disability, cerebellar ataxia, whole brain and cerebellar MRI-measured white matter volume and lesion load. Single-feature metrics independently contributed to an acoustic composite score that differentiated between mild, moderate, and severe levels of disability and correlated with EDSS scores in people with or without overt dysarthria (subclinical speech impairment. A similar ataxia acoustic composite score predicted an abnormal time to complete the 9-hole peg test with 85 percent accuracy, including in a naive dataset. Acoustic models were non-specific, with the same speech features compounding both the general and cerebellar models. Lastly, we observed wide differences in acoustic values for most speech features of interest between mobile devices and a professional recording set. Differences did not affect the relationship between acoustic scores and EDSS, although tested only in a small cohort. The current studies describe various speech acoustic features in their relationship with clinical disability and neuroimaging metrics in the same participants and further explores subpopulations of interest according to disability level and presence of dysarthria. Present results support the validity of speech models to, at least in part, reflect neurological status in MS. Current and previous findings strongly suggest against the interchangeable use of recording methods, particularly between different microphones and different distances between microphone and sound source, but do not preclude the use of mobile devices for health-related speech data acquisition.
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ItemExploring the aetiology of child speech and language disorders: Genes, brain and behaviour( 2020)Background Speech and language disorders are exceptionally common, affecting 1 in 20 children, yet we understand little about their aetiology. Advances in genetic analysis and brain imaging have increased our ability to unravel genetic contributions and brain-behaviour explanations for speech and language disorders. This PhD is focused on elucidating gene-brain-behaviour relationships, by refining the speech and language phenotypes of children with genetic and neural pathologies. Aims There were three main aims of the thesis, each forming a sub-study: Study 1. To conduct speech and language phenotyping of individuals and families, to drive targeted sequencing and identification of known and novel genes that cause speech and language disorders; Study 2. To conduct speech and language phenotyping of a cohort of individuals with pathogenic variants in FOXP1, a gene implicated in impaired communication; Study 3. To describe brain-behaviour associations between topography and severity of polymicrogyria (PMG) and speech and language ability. Methods Participants were recruited through research databases, clinical collaborators and online parent support groups. Speech and oral motor function, receptive and expressive language, non-verbal cognition and adaptive behaviour were assessed using a protocol of standardised tests. Clinical history, MRI data (Study 3) and cognitive assessments were analysed to interpret speech and language findings in the context of broader neurodevelopmental phenotypes. Results Study 1. 25 probands with severe or persistent speech disorder were referred to the study and 16 were included in the final analysis. Speech and language were characterised in all probands and 49 family members. DNA samples for these 16 probands were sent for whole exome or whole genome sequencing. Study 2. Speech and language assessments were completed in 29 individuals with pathogenic FOXP1 variants. All verbal individuals had a complex speech phenotype including dysarthria and broader motor planning and programming impairments and 88% had phonological errors. Language impairments affected nearly all participants, though abilities varied across the cohort. Study 3. 52 individuals with PMG were assessed and MRIs analysed. All verbal participants (regardless of their PMG pattern) had dysarthria, which ranged in severity from mild cases with subclinical features only, to more severe cases with no verbal speech. Developmental speech errors and language impairments were frequent, and profiles were more severe in individuals with perisylvian PMG and bilateral distribution of PMG. Discussion This PhD has important clinical implications for diagnosis, prognosis and clinical management of children with severe speech and language disorders. The detailed speech and language phenotyping here can assist clinicians in identifying individuals with severe speech disorders who may warrant genetic testing or brain imaging (e.g. to detect PMG) to elucidate the cause of their speech disorder. Novel information I have provided about the exact nature of speech and language phenotypes will also assist clinicians and families with prognostic counselling, and to understand the implications these conditions have for learning support and educational placement. Results can also be used to inform development of targeted therapy approaches for children with these genetic and neurological conditions. The discovery that very few patients were receiving targeted therapy (e.g. for dysarthria), highlights the urgent need for early referrals for evidence-based speech therapy.
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ItemSignificant Others and Vestibular Disorders: an exploration of Third-Party Disability( 2020)Vestibular disorders can have debilitating impacts on a person’s life, such as increased risk of falling, depression, and anxiety, among others. This may have impact on the lives of family members. Understanding the experiences of Significant Others (SOs) can assist health professionals in providing effective, family-centred management; however, little is currently known about the experiences of SOs in vestibular disorders. It is anticipated that SOs experience limitations to their daily functioning; a phenomenon known as Third-Party Disability. Third-Party Disability can be better understood by mapping impact to the World Health Organisation’s International Classification of Functioning, Disability and Health (WHO-ICF) framework. Understanding Third-Party Disability is crucial to tailoring management in this population and maximising functioning. Study 1: An exploration of significant others’ experience with ongoing vestibular disorders Aim: To understand the experiences of living with ongoing vestibular symptoms from the perspective of SOs. Method: Ten in-depth, semi-structured interviews were conducted with SOs of people with vestibular symptoms. A phenomenological thematic analysis was conducted to capture the essence of being a SO to somebody with ongoing vestibular symptoms. Key findings: Four themes were identified in the data. - Journey The progression of learning to understand, cope and adapt with a family member’s vestibular condition is a unique journey; - Ownership Participants reported varying levels of ownership of their family member’s vestibular condition; - Intangibility Participants reported inconsistent advice from healthcare professionals, struggles with understanding, and challenges obtaining a shared understanding with their own support networks; - Disempowerment SOs were left feeling powerless due to not knowing what to do for a family member when they experienced vestibular symptoms. Study 2: Third-Party Disability in ongoing vestibular disorders through the lens of the ICF framework Aim: To describe Third-Party Disability in SOs of people with vestibular disorders using the ICF framework. Method: Ten in-depth, semi-structured interviews were conducted with SOs of people with vestibular symptoms. Data were linked to the ICF framework. Key findings: SOs reported fewer social outings, psychological impact such as negative emotions, increased domestic responsibilities, and impeded leisure time, among other things. Modifiable contextual factors included healthcare professionals providing clearer information, increased support from social networks and better accessibility to medical care. Study 3: Involvement and Disability: a pilot validation of two surveys for significant others in cases of vestibular disorders Aim: To develop and perform pilot validation on two surveys to measure SO involvement and disability. Method: Two surveys (involvement and disability) were developed. Twenty-eight SOs responded to the surveys. Cronbach’s alpha analysis was conducted to determine internal consistency. Key findings (Involvement survey): Initial evaluation of internal consistency was non-ideal (Cronbach’s alpha=0.69) but with systematic omission of questions, adequate consistency was achieved (Cronach’s alpha=0.83). Key findings (Disability survey): Initial internal consistency (based on Cronbach’s alpha) was excellent (Cronbach’s alpha=0.96). No questions were omitted. Conclusions SOs experience marked changes in their everyday lives in the form of third-party disability. Healthcare professionals can address this problem by practicing family-centred care in vestibular consultations and measuring outcomes of family-centred management options using the tools developed in this study.
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ItemVoice changes in healthy adults over 50 years old( 2020)Voice changes occurring with ageing in the absence of disease are often referred to as presbyphonia. Despite attempts to describe this phenomenon, there is no established acoustic and perceptual profile of voice in healthy ageing populations. Diverse acoustic software programs have been used to acoustically describe older voices; however, the differences of acoustic measure outcomes make it difficult to clearly profile older voices. This thesis seeks to review our current understanding of acoustic and perceptual changes in voice across sex and age. It also generates novel data on these features in healthy adults over 50 years alongside measures of quality of life. One hundred and fifty one healthy adults over 50 years old were analysed with three different acoustic programs (48 acoustic measures), an auditory-perceptual voice assessment and voice-related quality of life questionnaire. Roughness, breathiness and tremor were key perceptual features identified in the cohort. Deviant acoustic features that varied across age included amplitude perturbation, frequency perturbation, spectral noise, tremor and cepstral/spectral parameters. Age was best predicted using a multiparameter feature metric (including amplitude perturbation, spectral noise and cepstral/spectral parameters). Acoustic and perceptual features correlated. There was some evidence that voice related quality of life is affected in healthy older adults. Vocal fold physiology and biomechanics were not investigated in this study, however clear differences in voice quality were observed in older age groups. These changes may be explained by biomechanical or structural changes to systems important for voice production including resonance, respiratory and vocal fold movement. We have brought together the disparate literature in this field and systematically investigated acoustic and perceptual features of voice in healthy older adults. These data provide a foundation on which to further explore the underlying mechanisms for change and establish a series of norms for current listener and objective studies into voice of adults with and without disease.
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