Measures of spectral change and their application to habitual, slow, and clear speaking modes.

Spectral measures are sensitive to dysarthric speech. However, it is unclear whether the spectral differences in dysarthric and healthy speech are due to slow articulation rate or reflect other qualitative changes in speech. Spectral measures were used to detect differences between habitual, slow, and "clear" speaking modes in 12 healthy speakers. Matched t-tests were used to determine differences in the rate and degree of spectral change between the speaking modes. Pearson's correlation coefficients were calculated to assess how well rate of spectral change predicts articulation rate (syllables per second). Clear speech had a significantly higher degree of spectral change than habitual speech, and slow speech had a significantly slower rate of spectral change than habitual and clear speaking modes. These differences occurred in all 12 speakers. The rate of spectral change was correlated with articulation rate across all speakers (range of r = .8-.9 within individual speaking modes) and therefore is a gross predictor of articulation rate. These results suggest that measures of the degree and rate of spectral change together can be used to detect changes between clear, slow, and habitual speaking modes, and hold potential as performance measures.