Aircraft noise dose-response relations for national parks

An analysis of visitor survey responses and concurrent noise exposure was performed using data from ten sites in four scenic U. S. National Parks. Data collection was structured to learn the effects of air-tour aircraft noise and high-altitude jet noise on the experience of park visitors at scenic overlooks and on short hikes. The analysis utilized multilevel logistic regression and resulted in six dose-response relations: two responses (annoyance and interference with natural quiet), paired with three response dichotomizations (slightly or more, moderately or more, and very or more). Each of those six relations retained the same set of regression predictors. Individual-visitor Leq from all aircraft (averaged over the visitor duration at the site) proved to be the most reliable/accurate predictor of all noise dose metrics tested. The relation with visitor Leq was significantly strengthened by inclusion of three additional dose-related predictors: the energy-percentage due to tour helicopters for each visitor, the same due to fixed-wing tour aircraft, and the interaction of these two percentages. In addition, the relation was also strengthened by inclusion of the following context variables: Scenic overlook or short hike, natural quiet very important (or not) to that visitor, visitor group includes only adults (or not), and first-time visit at that site (or not). For a given noise exposure, visitors expressed more negative response regarding interference with natural quiet than regarding annoyance. In addition, visitor response to a given dose of air-tour noise was less severe when there were low-to-moderate levels of high-altitude jet noise present.