To better determine the extent of noise pollution across the continental United States, Buxton, Wittemyer, and their colleagues analyzed recordings made at 492 national parks and other protected sites. To study the millions of hours of recordings, the team utilized a computer algorithm that allowed them to subtract estimated natural sound levels from existing levels.
“This gives you an idea of how anthropogenic noise affects the acoustic environment,” Buxton explained.
The results, published in the journal Science, show that human noise is doubling background sound levels in 63 percent of protected areas in the US where manmade disturbances are supposed to be reduced. A ten-fold or greater increase in background levels was identified in 21 percent of protected areas.
Such noise reduces the area that natural sounds can be heard by 50 to 90 percent. What could formerly be heard at 100 feet away can now only be heard from 10 to 50 feet.
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Even many remote wilderness areas were found to experience human-caused sounds at 3 decibels above natural levels.
“We found that aircraft and vehicles were the biggest culprits, with high noise pollution in protected areas near busy airports and with high densities of roads,” Buxton said.
Humans can become habituated to a certain level of noise pollution, “but noise that impacts communication and the ability to hear does not change over time,” Wittemyer said. He added that physical stress may also result from continued exposure to noise pollution.
Solving the problem is a tough challenge, which the researchers believe must be addressed at individual sites, at least for now.