Metallic Voice: Physiological and Acoustic Features

The metallic voice is usually confused with ring or nasality by singers and nontrained listeners, who are not used to perceptual vocal analysis. They believe a metallic voice results from a rise in fundamental frequency. A diagnostic error in this aspect may lead to lowering pitch, an incorrect procedure that could cause vocal overload and fatigue. The purpose of this article is to study the quality of metallic voice considering the correlation between information of the physiological and acoustic plans, based on a perceptive consensual assumption. Fiberscopic video pharyngolaryngoscopy was performed on 21 professional singers while speaking vowel [e]—in normal and metallic modes to observe muscular movements and structural changes of the velopharynx, pharynx, and larynx. Vocal samples captured simultaneously to the fiberscopic examination were acoustically analyzed. Frequency and amplitude of the first four formants (F1, F2, F3, and F4) were extracted by means of linear predictor coefficients (LPC) spectrum and were statistically analyzed. Vocal tract adjustments such as velar lowering, pharyngeal wall narrowing, laryngeal rise, aryepiglottic, and lateral laryngeal constrictions were frequently found; there were no significant changes in frequency and amplitude of F1 in the metallic voice; there were significant increases in amplitudes of F2, F3, and F4 and in frequency for F2; metallic voice perceived as louder was correlated to an increase in amplitude of F3 and F4. Physiological adjustments of velopharynx, pharynx, and larynx are combined in characterizing the metallic voice and can be acoustically related to changes in formant pattern.