UC Berkeley PhonLab Annual Report

The “many to one” problem arises when trying to map inversely from acoustic patterns tovocal tract configurations. In one famous demonstration, Atal et al. (1978) searched through theacoustic outputs of a synthetic vocal tract for vowels that matched each other exactly on the frequenciesof the first three resonances (F1-3) and found that for each vowel tested [i], [a] and [u] there wereseveral vocal tract configurations that gave the same formant frequencies. This result has been used toshow that one (whether speech technologist or listener) cannot inversely map from acoustics to derive aunique possible vocal tract shape. We synthesized vowels using the formant frequencies reported byAtal et al. and show that listeners can detect differences between them even though the vowels areidentical in the first three formants. Our conclusion is that listeners may not be as troubled by a manyto-oneproblem as has been assumed before.