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,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. >>>>>>>
Canary Songs All it takes to sing like a canary is good breath and muscle control. Simply by manipulating air pressure and muscle tension in its vocal organ, or syrinx, a canary can generate an amazingly varied repertoire of trills, warbles, and other melodic syllables.
This insight comes from a novel mathematical model of sound production in a songbird's vocal organ. Recent experiments suggest that a canary's syrinx generates sounds via vibrations of its labia—flaps of tissue that sit where a songbird's two bronchial passages meet its windpipe. The labia behave somewhat like a clarinet's reed, oscillating air that rushes past them. Muscles modify the stiffness of the labia and the width of the gap between the folds.
To develop their model of the syrinx, Gardner and his coworkers assumed that the labial folds act like a spring, moving back and forth to alter the size of the air passage. They also assumed that a canary uses just two mechanisms to control its vocalizations: changing the pressure of air from the lungs and modifying the stiffness of the folds. The researchers expressed their model in terms of a differential equation involving damped harmonic oscillators.
Computer simulations showed that by simply varying the air pressure and stiffness, it's possible to recreate much of a canary's rich repertoire. Indeed, some sequences of notes result from little more than a slowly changing phase relationship between oscillations governing air pressure and those controlling labial stiffness. Such cyclic behavior is characteristic of a wide variety of coupled oscillators.
"The starts, stops, and pauses between syllables, as well as variation in pitch and timbre, are inherent in the mechanics and can often be expressed through smooth and simple variations in the frequency and relative phase of two driving parameters," the researchers concluded.
In other words, it may not require a lot of brain power on the part of a canary to sing its heart out and attract a mate.
