Voice Source Variation Between Vowels in Male Opera Singers

Area of Science:

• Acoustic Phonetics
• Voice Science
• Speech Production

Background:

• Nonlinear source-filter interaction theory posits that vocal tract acoustics influence the glottal voice source.
• This interaction is predicted to be dependent on the frequency relationship between vocal tract resonances (formants) and laryngeal vibration frequencies (partials).

Purpose of the Study:

• To experimentally investigate the influence of the frequency distance between the first formant (F1) and its closest partial on the glottal voice source.
• To verify the predictions of nonlinear source-filter interaction theory in singing.

Main Methods:

• Professional opera singers recorded vowel sequences at four pitches and consistent loudness.
• Audio and electrolaryngograph (ELG) signals were recorded; audio was inverse filtered to extract voice source parameters.
• Relationships between voice source parameters (e.g., contact quotient, maximum flow declination rate) and F1-partial frequency distance were analyzed.

Main Results:

• Significant differences in contact quotient across vowels were observed at all four pitches.
• Significant differences in maximum flow declination rate (MFDR) were found at three pitches.
• Other voice source parameters showed differences at one or two pitches, and no consistent correlation was found between MFDR and the F1-partial frequency distance.

Conclusions:

• The glottal voice source exhibits variations across different vowels, supporting the concept of source-filter interaction.
• These observed voice source variations do not appear to be dependent on the frequency proximity of the first formant to its nearest partial.