Integrality in the perception of tongue root position and voice quality in vowels

In English and a large number of African and Southeast Asian languages, voice quality along a tense-lax dimension covaries with advancement of the tongue root in vowels: a laxer voice quality co-occurs with a more advanced tongue root. As laxing the voice increases energy in the first harmonic relative to higher ones and advancing the tongue root lowers F-1, the acoustic consequences of these two articulations may integrate perceptually into a higher-level perceptual property, here called spectral ''flatness.'' Two Garner-paradigm experiments evaluated this interaction across nearly the entire range of tense-lax voice qualities and a narrow range of F-1 values. The acoustic consequences of laxness and advanced tongue root integrated into spectral flatness for tenser and laxer but not for intermediate voice qualities. Detection-theoretic models developed in earlier work proved highly successful in representing the perceptual interaction between these dimensions. (C) 1997 Acoustical Society of America.