FAU researchers investigate the internal structure of vocal cords

How do our voices generate sound? Even though we use our voices every day, this has been the subject of very little research up to now. In the “Structure2Sound” project, researchers at Friedrich-Alexander-Universität Erlangen-Nürnberg (FAU) hope to discover more about the internal structure of our vocal cords. The German Research Foundation (DFG) and the Austrian Science Fund (FWF) are providing approximately 674,000 euros in funds for the project, which is being carried out in Germany and Austria.

A person’s voice can permanently change after surgery, radiotherapy treatment or due to age. This is often caused by scarring on the tissue of the vocal cords, which affects how they vibrate and changes the sound of a voice. The German-Austrian research project “Structure2Sound” is investigating how the internal structure of vocal cords affects these vibrations.

The project is focusing on what is known as the extracellular matrix of the vocal cords, which is a network comprised mainly of collagen, elastin and hyaluronic acid. These components influence the movement of vocal cords. “How this works and which role the individual components play is what we hope to find out”, explains project leader PD Dr. Marion Semmler from the Department of Phoniatrics and Pediatric Audiology at Uniklinikum Erlangen at Friedrich-Alexander-Universität Erlangen-Nürnberg (FAU).

Targeted modification of individual components

For their investigations, the scientists used pigs’ larynxes, which are a byproduct in abattoirs. “The structure and vibration behavior of the vocal cords of pigs are very similar to those of human vocal cords”, explains PD Dr. Semmler. “They are therefore particularly well suited for investigating how individual components affect the voice.”

Using special enzymes, the researchers destroy collagen, elastin or hyaluronic acid in the tissue. They subsequently investigate how the missing components affect vibrations. In a test setup, a compressor is used instead of the lungs to pass air through the larynx. High-speed cameras, acoustic measurements and pressure sensors record when the vocal cords begin vibrating, how regularly they move and how the base tone changes.

International and interdisciplinary collaboration

While the team in Erlangen is investigating how changes to the extracellular matrix influence the vibration behavior, the Austrian project leader Dr. Raphael Lamprecht from the Institute of Measurement and Sensor Technology at UMIT TIROL is developing new measurement techniques for examining the tissue.

The combination of these two approaches enables the researchers to systematically investigate the relationship between the inner structure of the vocal cords, their material properties and their vibration behavior.

Perspectives for new treatments

In the long term, the results could help patients whose vocal cords are scarred after surgery, injury or radiation therapy. “Such scar tissue often contains a large quantity of disorganized collagen. This means it is unable to vibrate freely”, says PD Dr. Semmler. “For example, a feasible approach would be use these new findings to destroy specific structures, thus enabling the body to rebuild the tissue again in an orderly manner.”

Age-related changes to the voice, paralysis of the vocal cords or targeted adjustment of the pitch of the voice could benefit from the research findings in future. “If we know which components are crucial for which vocal characteristics, we will be able to offer much gentler treatments for patients in the future,” says PD Dr. Semmler.

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