Giving rheology a voice
Written by: Steve Carrington
Choirs and glee clubs seem to be the in thing these days. I think its great people can get together socialize and express themselves through their music and there is room for everyone regardless of talent. Do you like to sing? Well maybe it’s not for everyone. But just consider for a moment where you would be without your voice…
Some people rely on their voice for their livelihood. And not only singers, this includes school teachers, ministers, preachers, lawyers and a whole raft of other professionals.
The Department of Communication Sciences & Disorders at the University of Iowa carries out research into the function of the human vocal folds aimed at understanding the viscoelastic properties that directly affect their ability to vibrate. This research relies to a great extent on making accurate rheology measurements.
Rheometry to the rescue
Rheology allows the researchers to gather data on how the larynx cells respond to vibrations at different physiological frequencies over a set period of time. Using a Gemini rheometer coupled to a specially designed piezoelectric driver they can characterize the viscoelastic properties of the human vocal folds (cords) across the frequency range from 1 to 2000 Hz. It is confidence in the base rheometer that allows overlap data to be collected in the lower frequency range – 0.01 to 100 Hz – in order to verify the high frequency data. By simulating vocal stresses from everyday conversation through to sustained over use, data can be obtained which reveals how cells in the larynx respond to particular speech patterns.
Changing the voice or voicing the change
Many human voice complaints arise from a change in the structure of the vocal fold tissues due to soft tissue complaints (nodule, polyp or scarring) and the voice can become very harsh and rough. Treatment to soften the voice usually involves injections of material into the core or lamina propria (Reinke’s space) of the vocal fold to modify the properties of the tissue and this relies on using an injectable carbomer hydrogel with predictable and stable viscoelasticity. Rheology measurements allow injectable materials to be designed which can modify the vocal fold tissue and produce the native properties required for their vibrational function to be restored.
Of course, by furthering our understanding of vocal fold function, this work also has the potential to develop techniques that may prevent voice damage in the first instance. For more information on this research please read the recent press release: University of Iowa’s vocal fold research keeps teachers talking