Acoustic analysis of vowels in patients with Parkinson\u27s disease

Parkinsonova bolezen je nevrodegenerativna bolezen, pri kateri se pogosto pojavijo težave z govorom oziroma hipokinetična dizartrija. Ta je lahko eden prvih znakov bolezni, njene značilnosti pa so med drugim monoton govor, tih, hripav glas in otežena izgovarjava. Logopedi, ki pri bolnikih ocenijo in zdravijo dizartrijo, se pri svojem delu večinoma zanašajo na lastno zaznavanje in subjektivno oceno govora. Za boljše zaznavanje odstopanj v govoru bi lahko pri ocenjevanju uporabljali akustično analizo govora, saj je ta bolj občutljiva in daje natančnejše rezultate. V tujini se za proučevanje samoglasnikov pri dizartričnem govoru pogosto uporabljajo meritve samoglasniškega artikulacijskega polja. Ker pa so te zelo občutljive na govorčeve osebne značilnosti (spol, starost …), so raziskovalci razvili meritvi indeks artikulacije samoglasnikov in razmerje centralizacije formantov, ki se opirata na razmerja formantnih frekvenc. V magistrski nalogi smo z akustično analizo proučevali izgovor samoglasnikov pri osebah s Parkinsonovo boleznijo. V raziskavi je sodelovalo pet slovenskih govorcev s Parkinsonovo boleznijo, tri ženske in dva moška, stari od 53 do 73 let, s trajanjem bolezni od 1 do 10 let. Za kontrolno skupino smo poiskali zdrave govorce, ki se ujemajo po starosti in spolu. Posneli smo njihov govor pri branju in spontanem govoru. Posnetke smo s pomočjo programa PRAAT analizirali in za vsakega govorca pridobili frekvence prvega in drugega formanta za robne samoglasnike (/i/, /a/, /u/). Izrisali smo samoglasniški trikotnik vseh govorcev ter izračunali trikotno samoglasniško artikulacijsko polje in indeks artikulacije samoglasnikov. Dobljene rezultate smo primerjali med govorci s PB in ujemajočimi zdravimi govorci. Uporabili smo neparametrične statistične teste. Izsledki instrumentalne analize so pokazali, da na osnovi vrednosti formantov govorci s Parkinsonovo boleznijo samoglasnik /a/ izgovarjajo višje v ustni votlini, samoglasnik /u/ pa bolj naprej kot ujemajoči zdravi govorci. Večina govorcev s Parkinsonovo boleznijo je imela manjše samoglasniško artikulacijsko polje in manjše indekse artikulacije kot zdravi govorci, čeprav te razlike niso bile vedno statistično pomembne. Ugotovili smo, da v prostem govoru indeks artikulacije samoglasnikov bolje razlikuje med zdravimi in bolnimi govorci kot samoglasniško artikulacijsko polje. Razlike med skupinama so bile pri branju večje kot v prostem govoru in je torej naloga branja bolj diskriminativna. S študijo smo zajeli akustično–artikulacijske značilnosti samoglasnikov oseb s Parkinsonovo boleznijo in izpostavili razlike z zdravimi govorci. Pridobljeni rezultati predstavljajo začetek akustičnih raziskav dizartričnega govora v Sloveniji in izhodišče za nadaljnje raziskovanje. Pripomorejo tudi k boljšemu razumevanju sprememb v govoru oseb s Parkinsonovo boleznijo in so spodbuda logopedom, da bi v svoje delo vključili tudi objektivne načine ocenjevanja govora. K akustični analizi bi lahko priključili še druge fonetično-fonološke metode, predvsem vezane na artikulacijo (ultrazvočna analiza).Parkinson\u27s disease is neurodegenerative disease that often causes motor speech disorder, named hypokinetic dysarthria. Speech difficulties include decreased volume, hoarseness, monotonous tone and imprecise articulation. These can be the first sign of the illness. Speech and language therapists usually relay on auditory-perceptual judgements for the assessment and treatment of dysarthria. Acoustic analysis of speech could be used for more precise detection of speech deviations, as it is more sensitive and gives more accurate results. One of the most frequently used measures for studying the articulation of vowels in dysarthric speech is Vowel Space Area. However, this measure is highly sensitive to inter-speaker variability. To overcome these disadvantages, scientists introduced two alternative acoustic metrics: Vowel Articulation Index and Formant Centralization Ratio. The study aimed to use acoustic analysis for exploring vowel articulation in Parkinson’s disease speakers. We included five Slovenian speakers with Parkinson’s disease, three women and two men. They were 53 to 73 years old and were diagnosed between 1 to 10 years ago. Five age-matched and gender-matched healthy speakers were recruited as a control group. Each participant was recorded while reading a passage and in spontaneous speech. Recording samples were then analysed in PRAAT and frequencies of the first and second formant of corner vowels (/i/, /a/, /u/) were measured. We drew the vowel triangle and calculated Triangular Vowel Space Area and Vowel Articulation Index for all speakers. With nonparametric statistical tests we compared data from parkinsonian speakers with data from matched healthy controls. The results indicate that speakers with PD produce vowel /a/ higher in the oral cavity and vowel /u/ more forward, than matched control speakers. The majority of speakers with Parkinson’s disease had a smaller Vowel Space Area and lower Vowel Articulation Index than healthy speakers, although the differences between groups were not always statistically significant. We found that Vowel Articulation Index differentiated between the two groups in both speech tasks and Vowel Space Area only in reading. The reading task thus seems to be more appropriate for uncovering speech characteristics of persons with Parkinson’s disease. In the thesis we examined acoustic-articulatory characteristics of vowels in Parkinson’s disease and pointed out the differences between healthy speech articulation. The obtained results represent the beginning of the acoustical analysis of Slovenian dysarthric speech and the starting point for further research. They also contribute to a better understanding of changes in speech due to Parkinson’s disease and are an incentive for speech and language therapists to include objective assessment methods in their everyday work