Vowel and consonant identification at high pitch: The acoustics of soprano unintelligibility

Sopranos are notoriously difficult to understand. This study tracks the progressive loss with extreme high f0 of (a) vowel quality distinctions, and (b) the percept of a syllable-initial lateral. A soprano sang [lV] syllables on the notes of an arpeggio from A4 to A5. V ranged over [i, ɛ, a, ɑ, ɔ, u, əә]. She performed as a phonetician, not a trained singer, so that aesthetic adjustments of vowel configuration were avoided to isolate the effect of f0. Twenty-seven students with IPA training responded on a forced-choice vowel quadrilateral, reporting also whether [l] was present. At the highest f0, all vowels sounded open and lateral detection was erratic. Findings are discussed with reference to acoustic analysis. Loss of spectral peak definition is argued to explain the results, but at intermediate pitches there is some recoverability of vowel articulation thanks to differing relative amplitudes in the first three harmonics.