快猫短视频

CANARIES warble in much the same way that opera singers belt out an aria, a
simple physical model of the birds鈥� singing technique has shown. This might mean
they can produce intricate songs with very little input from the brain.

Most animals can produce a full repertoire of sounds right from birth, but
songbirds have to learn from scratch. Just as human infants learn to master
language, the birds acquire complex songs from those around them. Canaries
raised in isolation make an unpleasant rasping sound.

Marcelo Magnasco, Tim Gardner and colleagues at Rockefeller University in New
York and the University of Buenos Aires in Argentina wondered how birds become
such accomplished vocalists. They decided to make a simple computer model of a
bird鈥檚 voice box to see if it could recreate song-like sounds.

When birds sing, they force air from the lungs past a flap of tissue called
the labia. The team modelled the labia as a simple spring and assumed that, as
it oscillates, the hole that the air rushes through changes size.

The pitch of the sound depends on the frequency of oscillation and the speed
with which air is forced out. These depend in turn on the tension in the labia
and the air pressure in the throat. 鈥淥ur general philosophy was to strip the
model down to the bare minimum,鈥� says Magnasco.

The approach paid off. Gardner found he could get the team鈥檚 model to
reproduce any type of canary song, simply by varying the labial tension and the
bronchial air pressure. This is similar to the way opera singers produce vowels,
by modulating the tension in their vocal cords and the force with which they
breathe out.

The result doesn鈥檛 prove that this is all there is to it. But Franz Goller,
who studies birdsong at the University of Utah in Salt Lake City, says it鈥檚 a
reasonable bet. If birds do sing this way, it may mean that only simple neural
impulses are needed to generate very complex songs.

The model may also throw light on how humans produce speech sounds. Magnasco
believes that a more complicated model could reproduce the intricacies of human
speech. That would mean we only need to produce fairly simple neural impulses to
control our voices when we speak. Of course, what humans say with their voices
is a different matter. 鈥淲e don鈥檛 think birds are communicating a meaning when
they sing,鈥� says Gardner.