William E. Robert
Harris Miller Miller & Hanson, Inc., 15 New England Executive Park, Burlington, MA 01803
The responses of over 750 national park visitors to sounds of aircraft overflights were measured at six study areas in the Grand Canyon, Hawaii Volcanoes, and Haleakala National Parks. Park visitors were observed as they entered each study area, and were asked to participate in a brief survey as they exited the area. The survey included questions about the visitor's reasons for visiting the park, and asked visitors to rate their responses to aircraft sounds on five-point scales. Simultaneously, in one to three positions representative of the study area, A-weighted sound levels were recorded at 1-s intervals using extremely low noise instrumentation. In addition, human observers maintained time-synchronized logs of aircraft audibility, types of aircraft audible, types of background sounds, and other factors. Several mitigating variables, such as background sound level and visitor expectations, were tested for their ability to improve the dose-response relationships. Logistic regression was used to generate four separate dose-response relationships, relating two visitor responses (annoyance due to aircraft sounds, and interference of aircraft sounds with natural quiet) to two acoustic doses (percentage of time aircraft are audible, and aircraft A-weighted equivalent sound level). [Work supported by National Park Service.]