- The Washington Times - Friday, June 3, 2005

GRAND CANYON NATIONAL PARK, Ariz. (AP) — Mounted at about ear level on tripods, microphones are capturing the sound of quiet at the Grand Canyon.

The four microphones are attached to sound-level meters and computers that later will screen out all man-made sounds, such as the chatter of hikers, the rumble of cars and the buzz of sightseeing planes and helicopters. All that will be left will be the sounds of nature: the wind in the trees, the chirping of birds.

Park officials are doing this because they need to establish the natural decibel level at the Grand Canyon before policy-makers can decide whether the current noise-reduction regulations governing flights over the park are adequate.

Although the listening devices are new, the effort to determine whether the park is as quiet as it should be goes back a generation.

Congress said in 1975 that natural quiet is a resource at the Grand Canyon, just like the animals and the vegetation, and must be protected.

At the time, flights over the canyon virtually were unregulated. But little was done about the aircraft until a helicopter and a sightseeing plane collided 2,000 feet above the canyon floor in 1986, killing 25 persons.

The federal National Parks Overflights Act was passed the following year, establishing flight corridors, altitude requirements and caps on the number of flights. The law also required that natural quiet be restored substantially to the park.

The problem was that no one defined “substantial restoration,” and no one knew what “natural quiet” sounded like at the canyon. That has contributed to years of fighting among air tour operators, environmentalists and policy-makers.

What constituted substantial restoration of quiet remained unsettled until 1994. The standard was set at half or more of the park having no audible aircraft noise at least 75 percent of the day. That did not settle the issue, though.

“Even what we meant by the ‘day’ was a contentious issue for many years,” said Ken McMullen, overflights and natural soundscape manager for the park. Officials finally defined “day” as 7 a.m. to 7 p.m.

But without knowing what decibel level constitutes “natural quiet” at the Grand Canyon, it is impossible to say whether substantial restoration has occurred.

So in April, canyon officials began gathering data using microphones placed away from developed areas of the park. The sounds will be plugged into a computer model that will determine the Grand Canyon’s natural decibel level.

By next winter, Grand Canyon officials should have an idea of how close they are to natural quiet in the summer and whether the current regulations are adequate.

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