Source-filter interaction: A study using vocal-tract data of a soprano singer

Abstract

When the fundamental frequency of voice is close to a formant frequency, the voice-source system in the larynx and the acoustic filter of the vocal tract can be coupled acoustically. This source-filter interaction (SFI) can cause unsteadiness in vocal fold oscillations, sudden jump of the fundamental frequency, and transitions in voice register. In this study, a magnetic resonance imaging device was used to scan the vocal tract of a soprano singer in three dimensions when she produced sustained vowels with different notes ranging from A3 (220 Hz) to A5 (880 Hz). The cross-sectional area and the input impedance of the vocal tract were then determined from image data. As a result, the frequency and the magnitude of the first impedance peak for the /i/ vowel increased when the note became higher, suggesting that a strong source-filter interaction may take place for high notes when the fundamental frequency is close to the peak frequency. We therefore conducted a computer simulation of voice generation using models of the vocal folds and the vocal tract. Our preliminary results showed different SFI effects depending on the magnitude of the impedance peak. [This work was supported by JSPS KAKENHI Grant No. JP16K00242.]