Amanda Rapoza

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.

GROUND EFFECTS IN FAA'S INTEGRATED NOISE MODEL

The Federal Aviation Administrations Integrated Noise Model (INM) has used a lateral attenuation algorithm based on the two regression equations described in the Society of Automotive Engineers Aerospace Information Report 1751 since 1981. These equations, which together represent a single relationship developed from measured data for 1960s and 1970s aircraft with low-bypass ratio jet engines, are applied equally in the INM to the entire fleet and do not take into account the effects of propagation over acoustically hard terrain such as water. For these reasons, the INM development team initiated the task of revising the lateral attenuation algorithm within the model in 1997. An entirely new methodology for considering ground effects is the primary component of the revised algorithm. The methodology, which is based upon a newly-compiled spectral data base, along with the physical acoustics model documented by Tony Embleton, Joe Piercy and Giles Daigle of the National Research Council of Canada, will exist in INM as a library of regression equations. As such, this approach will offer the accuracy and flexibility of a pure physical acoustics model, coupled with relatively modest computer runtimes. The methodology summarized in this paper will result in an improvement in the INMs predictive accuracy, especially at small reflection angles. It also provides the INM user with the ability to take into account the effects of an acoustically hard surface, including the effects of mixed, acoustically soft and hard ground surfaces, a capability never before available in this model. Recent field studies have shown the approach to agree well with measured data.

Aircraft noise‐dose‐visitor‐response relations for national parks.

The U.S. National Parks Overflights Act and the Air Tour Management Act require management of air tours over national parks. Unfortunately, past noise‐dose‐response relations do not suffice for predicting response of national park visitors who are not at home, are not exposed for months/years, and are not subject to jets on approach or departure, but instead to low‐flying tour aircraft. Toward filling that insufficiency, this study was designed to understand the complex relationship between in‐park noise exposure and park‐visitor response. The study derives from a decade of visitor surveys and simultaneous sound measurements at ten frontcountry sites (scenic overlooks and short hikes) within four scenic national parks. This talk describes the analysis of these measurements and documents the six resulting dose‐response relations—‐two responses (annoyance and interference with natural quiet and sounds of nature) paired with three response dichotomizations (slightly to extremely, moderately to extremely, and...

Wayside noise measurement and propagation predictions for four motorcycles categories

Motorcycle noise is distinct from other types of road transportation noise and it varies within this general vehicle type based on design characteristics. One-third octave band sound levels that had been measured for four motorcycles categories (cruiser, sport, dual purpose, and touring) using statistical, isolated pass-by techniques for wayside measurements were analyzed. The spectra are dominated by different frequency components depending on the category and these differences have implications on how sound for different categories propagates over extended distances. This is an important consideration for predicting and mitigating motorcycle noise. To illustrate this, these measurements were used to modify a version of the Federal Highway Administrations Traffic Noise Model. This model was then used to predict noise levels at various distances representative of typical receptor locations for the different motorcycle categories. It is expected that accounting for these differences will aid local, state and federal agencies that wish to improve the management of motorcycle noise in their jurisdictions.

Modeling and mapping aircraft noise in National Parks

Commercial air tours are a common source of noise within many national parks, affecting natural and cultural resources as well as visitor experience. To facilitate interactive modeling and mapping of air tour noise exposure, the Volpe National Transportation Systems Center and National Park Service (NPS), in cooperation with the Federal Aviation Administration (FAA), have created an Aviation Noise Analysis and Mapping Tool. This tool contains a library of park noise maps generated by modeling single aircraft operations on routes flown by that aircraft. The creation of this library is computationally intensive and requires considerable expertise to properly configure and run the models. With this tool and library, a broad range of users can interactively explore composite noise exposure generated by air tour traffic scenarios. Composite noise exposure is calculated by summing, across all aircraft and route combinations, the product of the number of flights on each route and the noise generated by each airc...

Aircraft dose-response research in National Park backcountry areas

The Federal Aviation Administration and National Park Service conducted joint research to better understand visitor response to noise from commercial air tour operations over units of the National Park System. Dose-response research in National Parks was conducted during the 1990’s at heavily visited, frontcountry sites. To expand this work, aircraft dose-response measurements were recently performed at seven backcountry sites in four National Parks. These sites provided both day and overnight hiking and camping opportunities, with visits ranging from one hour to several days. The sampling approach included side-by-side use of three survey instruments, enabling the evaluation of multiple response variables (annoyance, interference with natural quiet, and acceptability) and comparison of audio clip and in situ dose-response, along with the effects of wording and question order. The evaluation of visits longer than previously studied necessitated methodological enhancements including the use of global posit...

Aircraft dose-response relations for day-use visitors to backcountry areas in National Parks

The Federal Aviation Administration and National Park Service conducted joint research to better understand visitor response to noise from commercial air tour operations over units of the National Park System. Dose-response relationships developed for heavily visited, frontcountry sites in National Parks showed significant differences in responses between visitors to overlook and short-hike sites, suggesting that activity and visit duration are key influences. An extensive recently collected dataset from backcountry day-use visitors was utilized to further explore these and other influences on dose-response relationships. In this second of two papers on this research, we describe the model-fitting approach used to identify the combination of noise exposure metrics (dose variables) and mediator variables that best predict visitor responses to aircraft noise. The interpretation and application of the best fit model is presented along with the previously developed front-country model. Such dose-response rela...