No AccessJournal of Speech, Language, and Hearing ResearchResearch Article1 Feb 2017

Assessing Vowel Centralization in Dysarthria: A Comparison of Methods

    Purpose

    The strength of the relationship between vowel centralization measures and perceptual ratings of dysarthria severity has varied considerably across reports. This article evaluates methods of acoustic-perceptual analysis to determine whether procedural changes can strengthen the association between these measures.

    Method

    Sixty-one speakers (17 healthy individuals and 44 speakers with dysarthria) read a standard passage. To obtain acoustic data, 2 points of formant extraction (midpoint and articulatory point) and 2 frequency measures (Hz and Bark) were trialed. Both vowel space area and an adapted formant centralization ratio were calculated using first and second formants of speakers' corner vowels. Twenty-eight listeners rated speech samples using different prompts: one with a focus on intelligibility, the other on speech precision.

    Results

    Perceptually, listener ratings of speech precision provided the best index of acoustic change. Acoustically, the combined use of an articulatory-based formant extraction point, Bark frequency units, and the formant centralization ratio was most effective in explaining perceptual ratings. This combination of procedures resulted in an increase of 17% to 27% explained variance between measures.

    Conclusions

    The procedures researchers use to assess articulatory impairment can significantly alter the strength of relationship between acoustic and perceptual measures. Procedures that maximize this relationship are recommended.

    References

    • Baayen, R. H., Piepenbrock, R., & Gulikers, L. (1996). Celex2 (LDC96L14). Philadelphia, PA: Linguistic Data Consortium.
    • Boersma, P., & Weenink, D. (2012). Praat: Doing phonetics by computer. Version 5.3.04. Retrieved from http://www.praat.org/
    • Clopper, C. G. (2009). Computational methods for normalizing acoustic vowel data for talker differences.Language and Linguistics Compass, 3, 1430–1442.
    • Cox, F. (2006). The acoustic characteristics of /hVd/ vowels in the speech of some Australian teenagers.Australian Journal of Linguistics, 26, 147–179.
    • Diehl, R. L., Lindblom, B., Hoemeke, K. A., & Fahey, R. P. (1996). On explaining certain male-female differences in the phonetic realization of vowel categories.Journal of Phonetics, 24, 187–208.
    • Eadie, T. L., & Doyle, P. C. (2002). Direct magnitude estimation and interval scaling of pleasantness and severity in dysphonic and normal speakers.Journal of the Acoustical Society of America, 112, 3014–3021.
    • Ferguson, S. H., & Kewley-Port, D. (2007). Talker differences in clear and conversational speech: Acoustic characteristics of vowels.Journal of Speech, Language, and Hearing Research, 50, 1241–1255.
    • Fletcher, A. R., McAuliffe, M. J., Lansford, K. L., & Liss, J. M. (2015). The relationship between speech segment duration and vowel centralization in a group of older speakers.Journal of the Acoustical Society of America, 138, 2132–2139.
    • Fromont, R., & Hay, J. (2008). ONZE Miner: The development of a browser-based research tool.Corpora, 3, 173–193.
    • Hillenbrand, J. M., Clark, M. J., & Nearey, T. M. (2001). Effects of consonant environment on vowel formant patterns.Journal of the Acoustical Society of America, 109, 748–763.
    • Hillenbrand, J., Getty, L. A., Clark, M. J., & Wheeler, K. (1995). Acoustic characteristics of American English vowels.The Journal of the Acoustical Society of America, 97, 3099–3111.
    • Kim, H., Hasegawa-Johnson, M., & Perlman, A. (2011). Vowel contrast and speech intelligibility in dysarthria.Folia Phoniatrica et Logopaedica, 63, 187–194.
    • Kim, Y., Kent, R. D., & Weismer, G. (2011). An acoustic study of the relationships among neurologic disease, dysarthria type, and severity of dysarthria.Journal of Speech, Language and Hearing Research, 54, 417.
    • Lansford, K. L., & Liss, J. M. (2014a). Vowel acoustics in dysarthria: Mapping to perception.Journal of Speech, Language, and Hearing Research, 57, 68–80.
    • Lansford, K. L., & Liss, J. M. (2014b). Vowel acoustics in dysarthria: Speech disorder diagnosis and classification.Journal of Speech, Language, and Hearing Research, 57, 57–67.
    • Liu, H.-M., Tsao, F.-M., & Kuhl, P. K. (2005). The effect of reduced vowel working space on speech intelligibility in Mandarin-speaking young adults with cerebral palsy.Journal of the Acoustical Society of America, 117, 3879–3889.
    • Maclagan, M. (2009). Reflecting connections with the local language: New Zealand English*.International Journal of Speech-Language Pathology, 11, 113–121.
    • McRae, P. A., Tjaden, K., & Schoonings, B. (2002). Acoustic and perceptual consequences of articulatory rate change in Parkinson disease.Journal of Speech, Language, and Hearing Research, 45, 35–50.
    • Neel, A. T. (2008). Vowel space characteristics and vowel identification accuracy.Journal of Speech, Language, and Hearing Research, 51, 574–585.
    • Sapir, S., Ramig, L. O., Spielman, J. L., & Fox, C. (2010). Formant centralization ratio: A proposal for a new acoustic measure of dysarthric speech.Journal of Speech, Language, and Hearing Research, 53, 114–125.
    • Schiavetti, N., Metz, D. E., & Sitler, R. W. (1981). Construct validity of direct magnitude estimation and interval scaling of speech intelligibility: Evidence from a study of the hearing impaired.Journal of Speech, Language, and Hearing Research, 24, 441–445.
    • Sheard, C., Adams, R. D., & Davis, P. J. (1991). Reliability and agreement of ratings of ataxic dysarthric speech samples with varying intelligibility.Journal of Speech and Hearing Research, 34, 285–293.
    • Sussman, J. E., & Tjaden, K. (2012). Perceptual measures of speech from individuals with Parkinson's disease and multiple sclerosis: Intelligibility and beyond.Journal of Speech, Language, and Hearing Research, 55, 1208–1219.
    • Tjaden, K., & Wilding, G. E. (2004). Rate and loudness manipulations in dysarthria: Acoustic and perceptual findings.Journal of Speech, Language, and Hearing Research, 47, 766–783.
    • Traunmüller, H. (1990). Analytical expressions for the tonotopic sensory scale.Journal of the Acoustical Society of America, 88, 97–100.
    • Turner, G. S., Tjaden, K., & Weismer, G. (1995). The influence of speaking rate on vowel space and speech intelligibility for individuals with amyotrophic lateral sclerosis.Journal of Speech, Language, and Hearing Research, 38, 1001–1013.
    • Weismer, G., & Berry, J. (2003). Effects of speaking rate on second formant trajectories of selected vocalic nuclei.Journal of the Acoustical Society of America, 113, 3362–3378.
    • Weismer, G., Jeng, J.-Y., Laures, J. S., Kent, R. D., & Kent, J. F. (2001). Acoustic and intelligibility characteristics of sentence production in neurogenic speech disorders.Folia Phoniatrica et Logopaedica, 53, 1–18.
    • Young, S., Evermann, G., Kershaw, D., Moore, G., Odell, J., Ollason, D., … Woodland, P. (2002). The HTK-Book 3.2.: Cambridge, United Kingdom: Cambridge University Press.
    • Zraick, R. I., & Liss, J. M. (2000). A comparison of equal-appearing interval scaling and direct magnitude estimation of nasal voice quality.Journal of Speech, Language, and Hearing Research, 43, 979–988.

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