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Table 1. Noise disturbances affecting the percentage of the pop- ulation in Germany, according to the source and level of noise.
Delaney and his coworkers gave an example of an approach that may make such research possible. They report- ed on a study collecting continuous measurements of noise exposure to gopher tortoises using “on-board” monitoring devices. The goal of this study was to benefit the recovery and management of the gopher tortoise population under varying conditions, including exposure to military training operations.
Don Hunsaker and his coworkers reported on the effects of helicopter noise on the reproductive success of the coastal California gnatcatcher based on a 5-year field study of noise exposure with relation to reproductive success. Because the study was one of the first to collect an adequate sample of breeding attempts based on a priori analysis, it was possible to show that the “factors best predicting reproductive success were measures of suitable nesting habitat, not noise levels.” A. Bowles reported that preliminary analysis was showing a similar outcome from a 6-year study of breeding Mexican spotted owls exposed to low-flying military jet overflights. In that case, changes in flight routes by German Air Force coop- erators made it possible to demonstrate experimentally that habitat was a more parsimonious explanation for patterns of breeding success than exposure to aircraft.
In a study more comparable to research done on human speech interference, Susanna Blackwell and her coworkers examined the effects of sounds from an artificial oil produc- tion island on bowhead whale calling behavior over a three year period. Their analysis showed that an increase in tran- sient sounds from noise, for example, boats, resulted in sig- nificantly shorter calls. They also showed that that call detec- tion rates were dependent on the direction that the whales swam, suggesting that other perceptual features might be important, just as Schulte-Fortkamp and Dubois had described for humans.
Kathleen J. Vigness Raposa’s group described an effort to model the acoustic characteristics of exposures and marine wildlife responses using a system called the Marine Wildlife Behavior Database (MWBD). Their system is designed to assist environmental planners in estimating impacts of pro- posed new projects. The MWBD includes specific standards for measuring and characterizing behavior in a manner that allows movements or other behaviors to be integrated into models of noise propagation.
Metrics to characterize human responses to noise are still a subject of active investigation, even after over 40 years of research. Ambivalence about noise and noise effects in human soundscapes forces us to think about whether noise has only negative implications, such as annoyance, or whether features such as sound quality and previous experi- ence are important. Assessments that include multiple noise sources and sensory qualities will be needed for effective and
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continuum such as annoyance.
Richard Horonjeff introduced a hierar- chical method for single-observer, continuous sound source logging that has been applied in a number of national parks over the last 15 years. His method allows the relative impor- tance of exposures to human observers to be evaluated, something that is still a challenge in studies of animals whose behaviors are more difficult to translate into a perceptual
efficient evaluation.
From a comparative point of view, it is important to realize that nearly all of the effort to develop efficient met- rics has concentrated on only one of about 58,000 vertebrate species, all of which are thought to be capable of hearing (over 5,400 mammal, 10,000 bird, 8,200 reptile, 6,200 amphibian, and 28,000 fish species \[Integrated Taxonomic Information System, http://www.itis.gov/\]). Lacking species-targeted alternatives, much of the work on animals has been conducted using metrics designed for humans, but a number of session authors emphasized the risks of this approach. Mardi Hastings and her coworkers gave an excel- lent example by reviewing exposure metrics for evaluation of effects of sound on fish hearing. They described several studies indicating that the equal energy hypothesis does not apply when evaluating auditory effects of noise on fish.
West and his coworkers described the other side of the problem, the identification of outcome measures for animals. They reviewed the literature on potential noise impact on birds. They described that ‘takes’ (significant effects on indi- viduals) “can be physiological, behavioral, or ecological, but must be verifiably correlated with significant changes in species viability.” This aspect of the National Environmental Policy Act law underscores the greatest differences in studies of humans and animals—while mechanisms of injury to ani- mals may eventually prove to be similar to those identified in humans, the measurement of outcomes is different because impact on humans is assessed based on individual effects, while it is based on population-level effects in wildlife, such as effects on reproductive success.
Sheyna Wisdom referred to the role of science in assess- ing noise impacts on wildlife under the National Environmental Policy Act. Principles of adaptive manage- ment (management that changes with new information on impacts or population trends) are used by wildlife managers to implement policies. However, development of manage- ment methods is extremely challenging in the face of large data gaps. Managers must both protect wildlife and yet enable humans to function without unnecessary constraint.
Commonalities in impact research on humans and wildlife were clearer when research was conducted in areas where both humans and animals were impacted by noise. Kurt Fristrup gave examples of applying noise metrics in park lands managed by the U.S. National Park Service which is responsible for the experience of both humans and wildlife.
Noise as an Indicator of Quality of Life 37