Does the sound resonance in the windpipe change the voice source and the vocal fold oscillations?

What is it about?

Vocal fold oscillations are critical for producing the sound of voice. But the oscillations are highly complex. In normal in-vivo conditions, they are excited by air flowing from the lungs but are also influenced by interactions with the acoustic resonances of the subglottal tract (windpipe-trachea and lungs) and vocal tract (laryngeal, pharyngeal and oral cavities). We developed a special artificial subglottal tract supplying the air to the vocal folds which is free from acoustic resonances. We then connected the tract to excised larynges without any vocal tract. We proved that the physical vocal folds can self-oscillate and produce sound also without the subglottal and vocal tract interactions but their oscillations are different. Consequently, also their produced sound is different.

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Why is it important?

The mechanism of voice production is still not fully understood due to the hardly accessible location of the sound source inside the larynx and due to the complex structure-acoustic interactions of the vibrating vocal folds with the resonating cavities of the breathing airways. Here, we have developed a special windpipe for excised larynges where the acoustic resonances can be removed. This allows, for the first time, to investigate the real vocal fold oscillations and the voice source uder controlled conditions with or without structure-acoustic interactions. We show how do the vocal fold oscillations and the resulting sound differ when the interactions are removed, which is crucial for understanding the inherent vibratory properties of the voice source.