NATRUAL AND CULTURAL SOUNDS ARE INTEGRAL MEMBERS of the suite of resources and values that the National Park Service (NPS) is charged with preserving, restoring, and interpreting (NPS 2000). Results of research conducted in a variety of national park settings suggest that the quality of visitors’ experiences is tied to the naturalness of the area’s soundscape (Manning et al. 2006; Tranel 2006; Miller 2002). For example, findings from a recent study in Haleakala National Park in Hawaii suggest that the primary reason for visitors to take an overnight backcountry trip in the park is to experience the sounds of nature (Lawson et al. 2008). Human-caused sounds from aircraft, roads, maintenance activities, and other visitors, however, commonly permeate park soundscapes, making natural sounds and quiet an increasingly scarce resource (Krause 1999).

Recently, the National Park Service has applied indicator-based, adaptive management to address soundscape management and planning (Pilcher et al. 2008). This process involves formulation and long-term monitoring of soundscape indicators and standards of quality. Indicators of quality are measurable, manageable proxies for desired park conditions, and standards of quality are numerical expressions of desired conditions for indicators. As an example, the National Park Service might specify “human-caused noise-free interval duration” as an indicator of quality related to providing visitors opportunities to experience natural sounds and quiet. A standard of quality for this indicator might specify that at least 90% of visitors will experience at least one interval of 15 minutes or more that is free of human-caused noise while visiting the park.

Soundscape-related indicators and standards of quality are now being developed at a number of national parks, but measurement of some indicators, such as highly variable soundscape metrics, is nontrivial (Lawson and Plotkin 2006; Ambrose and Burson 2004). For example, natural sound levels fluctuate because of wind, air characteristics (e.g., density, temperature), and wildlife. Furthermore, visitors’ exposure to natural and human-caused sounds is difficult to observe directly or measure through visitors’ self-reports in surveys. However, visitor use and noise modeling technologies are potentially useful in this situation (e.g., Lawson and Plotkin 2006; Lawson 2006; Miller 2004; Roof et al. 2002).

The purpose of this article is to demonstrate the use of visitor use and noise modeling tools to provide spatially precise, integrated information about soundscape conditions within a national park setting. In particular, it presents research conducted at Rocky Mountain National Park, Colorado, to model and map visitors’ exposure to transportation-related noise while visiting attractions and hiking on trails in the Bear Lake Road corridor. The results of this work are expected to provide the National Park Service with a monitoring tool to track soundscape-related indicators of quality in Rocky Mountain National Park that is adaptable to other national park units.