Singing Like a Canary

Singing like a canary requires little thought, but simple actions, to yield complex vocal physics, researchers have found, yielding potential insights into how humans generate speech sounds.

Human speech and the songs of many bird species share a central similarity: the skills are not present at birth, but are only learned through early-life experiences.

To determine how brain activity leads to the production of sound, scientists strive to understand how much of the sound comes from complicated instructions from the brain and how much comes from complex physics of vocal organs.

Now, a US-Argentina research collaboration (Gabriel Mindlin, University of Buenos Aires, Gabriel@birkhoff.df.uba.ar) has designed a simple physical model that accurately reproduces notes of a canary song.

The researchers modeled the canary's vocal organ, called the syrinx. According to previous experimental evidence, the syrinx generates sound through vibrations of its labial "folds"---flaps of tissue which open and close the air passage between the throat and the lungs.

In their model, the researchers make the key assumption that these labial folds behave like a simple spring, moving back and forth to change the size of the air passage. They further assume that a canary controls its vocalizations through two actions: changing the pressure of the air from the lungs and using muscles to modify the stiffness of the folds.

By varying these two parameters, the researchers found that the spring-like labia could produce faithful recreations of three canary notes. Therefore, simple changes to a basic system, rather than sophisticated instructions from the brain, can reproduce the rich, complex vocal physics which give rise to complicated sounds. (Gardner et al., Physical Review Letters, 12 November 2001.)