Noise Inescapable in Some Flagship National Parks

A few times a year, Bryson Garbett loads up his family and heads to a national park, often one in southern Utah.

Part of the draw to a place like Zion -- aside from the hiking, rappelling and backcountry stargazing -- is that it's quiet.

Garbett, president of a home building company in Salt Lake City, is happy to swap the urban din for murmurings of frogs and birds or even flat, dead silence.

Almost always, though, that tranquility is broken by an airplane overhead or some other kind of man-made machinery