What is Normal?
Voice Rehabilitation depends on knowing to what degree we deviate from the norm. This helps us better understand what constitutes a disorder. A recent descriptive analysis was completed by Daniel Croake, Richard Andreatta and Joe Stemple looking at how the subsystems of voice (respiration, phonation and resonance) all interact in healthy normals.
Stemple and team wanted to look at how the three subsystems interact and what makes that interaction normal. Breath, vocal cord vibration and the space in the throat, mouth and nose are all complex, as are their interactions to manipulate sound production.
So two questions arose:
1) Can we look at the subsystem patterns in vocally normal individuals to measure them and describe them
2) Can we make any more specific findings to describe regarding differences of physiologic nature
What Was Observed?
We know there is not one specific vocal subsystem balance situation that fits every human. 29 vocally healthy young people 21 of whom were women were included in this study. (I find this balance for the study funny because it is true to what is increasingly a more common finding of more voice disorders in females than males.) All were strobed, had acoustics taken, and aerodynamic measures taken.
Findings were that 7 of the 9 things they measured, were different in a significant way. This is important because even among “normal” or what we see as normal, there were very different representations of it.
What is stunning about this study, is that we may feel that normal is constant or even predictable, but we really don’t know much about variables within the range of what is normal. Parts of the breathing and sound production system were strongly correlated, relationships were found between breathing and resonance as well. All their findings truly show that I will likely need to edit my current handouts about our 3 system model of phonation in a few years, but it will benefit our understanding of the systems.
Stemple and team suggest the model should reflect a more flexible view of vocalization regarding subglottic pressure and average airflow rate. Hard work from all who put this study together, thank you for always asking questions so we know more about how effectively we can help others for voice rehabilitation.
Descriptive Analysis of the Interactive Patterning of the Vocalization Subsystems in Healthy Participants: A Dynamic Systems Perspective Daniel J. Croake , Richard D. Andreatta and Joseph C. Stemple Journal of Speech, Language, and Hearing Research, Vol. 62, No. 2, February 2019: 215-228.
Abstract | Full Text | PDF (260.8 KB KB)