The same physical mechanism is behind the songs of birds and the words of humans, says a new study published in the journal Nature Communications.
The sound of human speech might seem very different from birds singing, but, the similarities that exist far beyond our eyes are stark. While humans produce sounds via the larynx, and birds via the syrinx (which is unique to them), the mechanism of the movement of the vocal cords are the very same.
The lead author of the paper, Dr. Coen Elemans from the University of Southern Denmark, explains that the myoelastic-aerodynamic theory (MEAD) which was previously known to apply to human speech and singing has now been shown to drive the making of vocalisation in birds too. Dr. Elemans even suggests that MEAD could possibly be more common than expected among vertebrates living on land.
When Dr. Elemans and his team studied sound production in 6 species of bird from 5 avian groups with high-speed cameras, they found that they all used the MEAD mechanism.
The MEAD goes as follows:-
In the larynx, air emanating from the lungs pushes past the vocal cords whose sideways back-and-forth movement makes the larynx open and close with each oscillation; sound pulses are thus created when the airflow is made to stop and start.
During one second of human speech, or song, hundreds or thousands of such oscillations occur. For each oscillation cycle, a wave travels from the lungs to the vocal chords to the mouth such that the oscillations are sustained.
The findings are surprising because the vocal organs are very different (the syrinx, for instance, is found deep in the body).
The authors also believe their findings imply that songbirds sharing another mechanism – the neural mechanisms underlying vocal learning – with humans can be used as a model to study neurological diseases pertaining to human voice. They hope to use their knowledge of songbird vocals for research purposes in the production of human ones.