An Acoustical Basis for Universal Phonotactic Constraints

Spectral characteristics of some selected phoneme sequences are investigated in an attempt to explain cross-linguistic tendencies in phonotactic constraints. A hypothesis is offered that some universal sequential constraints are acoustically motivated. Two acoustic factors are posited as determinants of favored/disfavored sequences: The magnitude of acoustic modulation within a sequence and the degree of acoustic difference between sequences. The hypothesis is tested experimentally for its applicability to some of the universal constraints. Trajectories of the first three formants are obtained for selected sequences of stop + liquid + vowel, stop + glide + vowel, stop + vowel, and vowel + stop. Standard Euclidcan distance in frequency is computed as a measure approximating each acoustic factor. The results show that some universally rare or unstable phoneme sequences can be explained on the basis of their lack of spectral modulation and/or their spectral similarity to other sequences, suggesting that acoustic/auditory factors play a significant role in determining the phonetic shape of language.