FAU researchers use artificial larynx to replicate individual vocal fold vibrations

Almost one in three people suffer from serious voice problems at some point in their lives – among teachers, it is even more than one in two. Functional dysphonia is often the underlying cause: The voice is chronically hoarse or fails, even though no discernible physical change is present. Using an artificial larynx, researchers at Uniklinikum Erlangen, Friedrich-Alexander-Universität Erlangen-Nürnberg (FAU) aim to make the causes of the disorder visible. The German Research Foundation (DFG) is funding the research project with around €300,000.

How does functional dysphonia develop?

Most people control their voice intuitively: The interplay of muscles in the larynx occurs largely unconsciously. Anyone who suddenly has to speak a lot therefore sometimes adopts unfavorable speech patterns without noticing it.

“Through such strain, the voice can permanently become hoarse or fail completely, even though nothing in the larynx is injured or diseased,” explains Prof. Dr. Stefan Kniesburges of the Department of Phoniatrics and Pediatric Audiology at Uniklinikum Erlangen. Experts refer to this as functional dysphonia. This condition accounts for around half of all voice disorders.

Understanding the causes of the voice disorder

Physicians can observe how the vocal folds move, but what happens inside the larynx in the process largely remains hidden. Via endoscopy, a medical imaging examination, the vibration of the vocal folds can only be observed from above.

“We are not yet able to investigate what happens below the vocal folds and how the airflow behaves in the larynx,” explains Prof. Stefan Kniesburges. Together with his research team, he therefore aims to make these flow and pressure conditions visible using an artificial larynx.

How does the artificial larynx work?

To identify the causes of functional dysphonia, the researchers replicate the vocal fold vibrations of individual patients in the model using high-speed footage from laryngeal endoscopy. An algorithm automatically adjusts the model until the artificial vocal folds vibrate exactly like those in the recording.

With the artificial larynx, the researchers can for the first time investigate how the vocal folds move, what airflows arise in the larynx, what pressure conditions prevail at the vocal folds, and how these processes relate to the sound of the voice.

How could the artificial larynx improve voice therapy?

In the long term, the model is intended to help tailor treatment more specifically to the individual needs of patients. “In voice therapy, patients learn to use their voice more consciously and more economically. Speech-language pathologists support them along the way with individually tailored exercises that promote body and voice awareness and improve the function of the vocal organ,” explains Prof. Stefan Kniesburges. “If we are able to track more precisely in the future which processes take place in the larynx of each individual patient, exercises and therapeutic measures can be selected even more specifically and tailored individually.”

To achieve this, the researchers are first developing and testing their model using healthy voices. This will then be followed by recordings from patients with functional dysphonia. In the long term, the model is intended to help improve understanding of how functional voice disorders develop and to create new scientific foundations for diagnosis and therapy.

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