An international team of scientists has solved the mystery of hummingbird hummingbirds

The beautiful thing about a hummingbird's intricate wing beat is that it creates a higher pitch, and it is these notes that give the sound its own character.

As soon as you hear its sound, you can immediately distinguish it from other types of birds, but the reason behind the hummingbird's hum has remained a hot mystery scientists have explained to this day.

In a report published in the Guardian newspaper (The Guardian) on March 16, the writer indicated that the main reason appears to lie in the forces of aerodynamics, and then the change in pressure produced when the wings are moved.

This is according to the results of research conducted by scientists from the American Stanford University and the Dutch Eindhoven University of Technology, in partnership with the Dutch company Sorama, and published in the journal eLife on March 6, 2021. , after experimenting with a species known as Anna's hummingbird.

While it was known that the hum was associated with the movement of the wings, the reason behind the sound was not clear, as it was likely that the pressure change caused by the flutter and the vortices generated in the air And the whistling of the feathers is the cause of the sound.

3D audio map

The team placed more than 2,000 high-speed microphones and cameras around a cage in which six hummingbirds were feeding on an artificial flower, allowing them to capture the birds' sounds and then create a 3D sound map, correlating it with the movement of the wings captured by the cameras.

To find out where the sounds came from, the team sought to measure the lift and friction forces caused by flapping wings. To do this, they created another experiment where the birds were surrounded by pressure gauges, as well as high-speed cameras, and watched them while flapping, quantifying the pressure forces produced and how they changed over time.

When the researchers combined information about the forces with the movement of the birds' wings, they were able to predict the sounds that would arise from these factors alone, and then compared them to the 3D sound map generated by the first experiment.

The results revealed that the aerodynamic forces generated during the movement of the wings, along with the speed and direction of the wings' movement, are largely sufficient to explain the hum.

The secret of the movement of the wings

The team noted that the critical factor is the movement of the hummingbird's wings. While most birds create lift only when the wing is downward - the team found it to be the primary sound source - hummingbirds do so in the wing movement down and up as a result of the unusual wing movement, which follows A U-shaped path.

Furthermore, these bangs occur much faster in hummingbirds (about 40 times per second), and as a result, the team says that the movement of a hummingbird's wing generates sounds at both 40 and 80 hertz, which they found to be the main components of humming.

But the fluctuation of forces in the wing strokes, and the effect of the movement of the U-shaped wing, generated higher frequency tones for these sounds.

“The beautiful thing about a hummingbird’s complex wing beat is that it causes a higher pitch, and it is these tones that give the sound its character. The special way the forces change creates the sound we hear,” he says to Lintick. “That alone is enough to understand the source." main tinnitus.

The team applied a simplified version of their theory to data on flying creatures, from mosquitoes to birds such as pigeons, to reveal why their movement produces different sounds. "It's the different way the thrust forces are generated, which gives each bird a different sound," he explains.