Increasing the intelligibility of sung vowels

The intelligibility of the front vowels (/i/, /I/, /epsilon/, and /ae/) was investigated as sung in four different ways: (1) operatic, (2) in consonant-vowel-consonant (CVC) context, (3) with a raised larynx, and (4) with both raised larynx and in CVC context. Al syllables were sung by a trained soprano at F4, A4, C sharp 5, F5, A5, and C sharp 6. Ten subjects listened and identified randomized sets of ten tokens of each vowel per condition (method of articulation) at each note. Results showed that, from C sharp 5 (nominal 554 Hz) to F5 (698 Hz), the intelligibility of operatic vowels (condition 1) fell from 56% to 16%. The mean intelligibility of the vowels at the three highest notes (F5, A5, C sharp 6) was 10% for condition 1, 64% for condition 2, 62% for condition 3, and 83% for condition 4. Results indicate that increased intelligibility across conditions is a function of increased energy in the higher harmonics and presence of consonantal transitions. The generally accepted notion that vowel sounds are largely unintelligible on higher notes pertains only to a restricted manner of production.