Individual Difference Of Relative Tongue Size And Its Acoustic Effects

This study examines how the speaker's tongue size contributes to generating dynamic characteristics of speaker individuality.The relative tongue size(RTS)has been proposed as an index for the tongue area within the oropharyngeal cavity on the midsagittal magnetic resonance imaging(MRI).Our earlier studies have shown that the smaller the RTS,the faster the tongue movement.In this study,the acoustic consequences of individual RTS values were analyzed by comparing tongue movement velocity and formant transition rate.The materials used were cine-MRI data and acoustic signals during the production of a sentence and two words produced by two female speakers with contrasting RTS values.In this paper,the existing MRI data and acoustic data were used to study the individualized differences caused by the relative size of the female,that is,the relationship between the size of the tongue,the movement of the tongue,and the rate of change of the formant frequency.The results indicates that the speaker with the small RTS value exhibited faster changes of tongue positions and formant transitions than the speakers with the large RTS values.To summarize,the RTS is reflected by tongue movement velocity and thus relevant to the varied rate of the changes in vocal-tract resonance.This acoustic effect results in the differences of the rate of formant frequency transition.Since the tongue size is uncontrollable by a speaker's intention,the RTS can be regarded as one of the causal factors of dynamic individual characteristics in the lower frequency region of speech signals.