Can sound protect the eagle from wind turbine impact?
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Every year, vultures and golden eagles die by accidentally hitting the blades of wind turbines. One way to prevent these accidents is to use sound signals to drive away these birds.
To determine which sound is most effective in deterring birds by earthquake, researchers at the University of Minnesota tested the vulture's behavioral response to a series of natural and synthetic sound stimuli.
Auditory neurologist JoAnn McGee will present the results of these tests at the 177th meeting of the American Acoustics Society at Galt House in Louisville, Kentucky, from May 13 to 17.
Three adult vultures were used in the study: two could not survive in the wild and lived permanently in the university ’s laboratory, and a bird was returned to the wild after receiving rehabilitation treatment at the center. Each bird was tested in a 9-foot by 7-foot space, which was covered with soundproof materials. Let it perch on a railing in the center of the room, with speakers on the left and right walls; a high-resolution camera is directly installed in front of the bird to capture its response to sound.
A total of 10 different stimuli were tested in the experiment, and their spectral complexity varied. These sounds include natural sound stimuli, such as the eagle's own calls, and synthesized sounds, including pure-tone stimuli, FM and AM stimuli, and white noise. McGee explained that the researchers also tested a new sound signal from the crow flock, which is the sound of crows that colonize or jointly attack other birds entering their territory.
Observers watching videos of these birds judge their reactions. For example, when playing sound stimuli, whether their heads move or tilt, or appear frightened. Perhaps not surprisingly, the eagle is more interested in natural calls than synthesized voice signals, and pays more attention to them. However, McGee said this is not to say that they do not respond to other relatively wide-ranging sound signals, including crow calls. She said: "Attention to the environment around them will have an important impact on their survival, so we are not surprised."
The study also shows that the daily hearing space of vultures and golden eagles belongs to a fairly clear frequency band, with the upper cut-off frequency of about 6 kHz and the lower cut-off frequency of less than 0.35 kHz. The researchers suggest that sound signal designers use these data as development guidelines in an effort to design effective and efficient acoustic deterrent systems.
McGee explained that the results of the project have taken a critical step in the development of acoustic alarm or deterrence technologies that may prevent the eagle from flying into the area where the wind power is located and reduce the damage and death caused by turbine collisions.
(Original source: Daily Wind Energy China New Energy Network Comprehensive)
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