Congress requires management of Grand Canyon air tours to provide for “substantial restoration of natural quiet.” Many areas of the Canyon are extremely quiet, and tour aircraft can sometimes be heard 10 to 15 miles from the air tour corridor.
A combination of on-site measurements and computer noise prediction modeling is critical to determining restoration of natural quiet. Because “substantial restoration” is determined by audibility of tour aircraft, models are needed that compute audibility.
From 1999 until 2002, HMMH developed and led a scientifically rigorous, peer-reviewed analysis of three different proposed computer prediction models. The validation is based on statistical analyses of the comparison of the modeling results with acoustic data collected in the Grand Canyon.
This is the first study of its kind designed and tested to accurately compute aircraft audibility in a park environment and at distances typical of the Grand Canyon.