Academic journal article Journal of Singing

Effect of Multifactorial Constraints on Intelligibility of Opera Singing (II)

Academic journal article Journal of Singing

Effect of Multifactorial Constraints on Intelligibility of Opera Singing (II)

Article excerpt

[Continued from Journal of Singing 63, no. 4 (March/April 2007)]


Relative Duration of Vowels and Consonants

In singing, the average duration of vowels is considerably longer than it is in speech, whereas that of consonants is slightly shorter (Figure 1). Voiceless consonants and vocalic consonants* have sung durations that are comparable to their spoken ones. Voiced consonants, whether plosives or fricatives, are shorter in speech than voiceless ones; this tendency is even more marked in singing, where voiced consonants are shortened to the point of becoming about half or a quarter as long as they are in speech, most likely because of physiological constraints of an aerodynamic nature (Figure 2). Indeed, too great a duration is thought to cause an overly large increase in the intra-oral pressure* which, by hindering vocal fold vibration, leads to devoicing.

One of the reasons the mean duration of consonants is lower in singing than in speaking is that while vowels supply an ideal support for the melody, as noted above, consonants interrupt the melodic line. This leads singers to shorten consonants by underarticulating them, as they strive to preserve the quality of the legato.1 Rostolland suggested that consonant shortening in singing may have a physical cause too. He noted the same phenomenon for shouted consonants, and accounted for the shortening in terms of the high intra-oral pressure that reigns in the vocal tract during consonant production. This pressure leads to a "more abrupt and more rapid opening of the buccal passage, particularly for plosive consonants."2 There are certainly other explanations for this phenomenon, but whatever the underlying reason, consonant shortening considerably lessens the intelligibility of opera lyrics.

Temporal Structure of Sung Syllables

In singing, the sizeable lengthening of syllables modifies syllabic makeup: the more a syllable is lengthened, the greater the vowel-to-consonant ratio. For example, if consonants in a spoken syllable take up half of the total syllable duration, they will represent only an eighth ofthat duration when that same syllable is sung. This phenomenon destroys the syllable's temporal balance.3 In French, the perception of the syllable as a phonetic unit is based on the law of syllabic isochrony, according to which all syllables tend to be of equal duration. Syllabic equality is achieved in speech by varying the relative lengths of the vowels and consonants within the syllable: when a consonant is very long in a spoken syllable, the vowel will be short, and vice versa. In singing, where rhythmic constraints impose different durations on sung syllables, syllabic isochrony cannot exist. For this reason and the fact that, according to Gestalt Theory*, perception is syncretic*, the anamorphoses* that vowel lengthening creates in the acoustic images of the syllable will hinder the recognition of global vocal forms*, not only at the syllabic level, but also at the word level.

Elasticity Limits of Vowels and Consonants

Consonants, like vowels, undergo an overall increase in duration when the tempo slows down, but unlike vowel durations that vary greatly, the extent of consonant lengthening is limited. This fact further jeopardizes syllabic equality (Figure 3). As a result of the physiologic constraints of production, the elasticity limits of consonants are practically identical in speaking and in singing, with a compression limit of 16 ms and an expansion limit of 324 ms in speech, as compared to 16 and 340 ms in singing (Figure 4). The compression limits of vowels are also very close in speaking and in singing, reaching 38 and 40 ms, respectively.4 As Duez stated, "the compression limit is imperative, since one must preserve message intelligibility and this requires maintaining phoneme identity, which among other things is based on duration: short of a certain duration, phoneme identity is destroyed. …

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