Academic journal article Journal of Singing

Resonance Strategies Revealed in Rock Singers during Production of High Notes

Academic journal article Journal of Singing

Resonance Strategies Revealed in Rock Singers during Production of High Notes

Article excerpt

INTRODUCTION

THE PHYSICAL CONCEPT OF RESONANCE requires that there be two systems, a driven system and a driving system. The driving system feeds energy into the driven system.1 In voice production, the driving system is the vibration of the vocal folds, and the driven syste m is the vocal tract. The vocal tract is responsible for radiating the sound, and it vibrates because energy is fed into it from the vocal folds.

The phenomenon of resonance requires that the driven system or resonator have some modes of vibration (resonance frequencies). Therefore, there are special frequencies where this driven system naturally vibrates. Resonance occurs when the driving system introduces acoustic energy into the driven system at one or several of these resonance frequencies. When the driven system is driven at a frequency that it "likes," this system responds "enthusiastically" and the amplitude of the resulting vibration can increase significantly.2 When the resonator is the human vocal tract, resonance frequencies are called formants. Thus, the ability of the vocal tract to transmit sound is at its greatest at the formant frequency peaks. In the vocal tract the four or five lowest formants are the most relevant ones.3

The acoustic theory of speech is usually applied to voiced sounds in the pitch range of speech, where the harmonics are dense enough to supply sound for any formant. Thus, the approximate location of the formants in the spectrum can be clearly revealed. On the other hand, in the singing voice the fundamental frequency (F^sub 0^) is commonly produced in a higher pitch range, often higher than the normal value of the first formant (F1). Therefore, the distance between the harmonics is greater. This wide spacing of the harmonics of higher fundamental frequencies requires careful tuning of the formants, which boosts a limited bandwidth of frequencies and loses effectiveness if located far from a harmonic. Vowel modification is usually the way to get an appropriate formant tuning in high pitches in the singing voice.4

Vocal tract resonances are highly adjustable by articulatory changes. Even within a given vowel category the first and second formant (F1 and F2) frequencies can vary as much as 50-100%. The bandwidth of the vocal tract formants normally ranges between 40 and 100 Hz. A bandwidth reduction increases the selectivity of the vocal tract and makes enhanced harmonics prominent, in the extreme case of overtone singing, even audible as discrete tones.5

Formant tuning through vowel modification leads to several resonance strategies that singers use to achieve an optimal sound without phonatory effort in high pitches. If a formant approaches a harmonic, the overall radiated sound level (SPL) is generally increased. This possibility to increase SPL and enhance the resonance qualities of a voice without expense of vocal effort is an attractive possibility from a singer's point of view.6

Several studies have been carried out to explain resonance strategies for singers when they increase fundamental frequency. Most of them have been performed in classically trained singers. Sundberg reported that a professional soprano increased the opening of the jaw as the pitch increased.7 According to him, the purpose of dropping the jaw was to keep the first vowel formant (F1) slightly higher than the fundamental frequency (F^sub 0^) to gain intensity by taking advantage of the resonance of the formant/partial interaction.8

A study to determine the dependence of jaw opening on pitch and vowel in singers supported earlier findings in that singers tried to avoid the situation where the F^sub 0^ was above the frequency of the first vowel formant (F1) in both male and female singers by either lowering the jaw or some other adjustments in the vocal tract such as a reduction of tongue constriction.9 Thus, the jaw opening seems to be an important-though not the only-tool for all singers, not just sopranos, trying to avoid having F^sub 0^ higher than F1. …

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