In the autumns of 2012 and 2013, any hikers walking along a particular ridge in Idaho’s Lucky Peak would have become very confused. One minute they’d be enjoying the tranquil chirps and rustles of a temperate woodland. The next, they’d be immersed in the unnervingly realistic sounds of a roadway: metal rushing past at speed, tires rolling over asphalt, honking horns. The nearest road, however, was several miles away. These noises were coming from 15 pairs of large bullhorn speakers that had been lashed to the trees. The hikers were walking along a phantom road.
This half-mile corridor of disembodied sound, this road in noise only, was the work of Jesse Barber and a team of scientists and volunteers from Boise State University. Their goal was to answer a simple question: How does the bustle of traffic affect the presence and health of birds?
Others studies have found that noisy man-made structures, from roads to natural-gas plants, can drive away wildlife and drown out their calls. But in all of these studies, noise was accompanied by other problems—pollution, the potential for collisions, and predators patrolling the roadsides. “No one had done the obvious thing: use speakers to simulate the noise component of a road and create a phantom road,” Barber said.
To do that, his team, including masters student Heidi Ware and postdoctoral researcher Christopher McClure, recorded the sound of a dozen cars zooming through Glacier National Park. They combined these recordings into a looping, minute-long clip, which represented the kind of traffic you’d get in some of North America’s most-visited national parks. They then unleashed this clip on a ridge in Lucky Peak State Park, where forests of mighty Douglas firs give way to lush bushes of chokecherries and bitter cherries. It took months of hiking and hard labor to set the speakers up correctly. “I got really good at carrying lots of heavy batteries,” says Ware.