The National Park Service manages 84 million acres of land spread across 397 national parks, 40 national heritage areas, and 582 national natural landmarks, all of which are collectively termed “national parks” in this report. The Park Service has the most wilderness acreage of the major wilderness management agencies (the others are the Fish and Wildlife Service, the Bureau of Land Management, and the Forest Service). It is also the only federal land management agency with a mandate to protect the acoustic environment, said Karen Trevino, chief of the Natural Sounds and Night Skies Division, one of eight divisions of the Natural Resource Stewardship and Science Directorate in the Park Service. “The mission [of our division] is to work to restore, maintain, and protect acoustical environments and naturally dark skies throughout the national park system,” she said in her introduction to the workshop’s opening plenary session. “We work in partnership with parks and others to increase scientific understanding and inspire public appreciation of the value and the character of undiminished soundscapes and star-filled skies.”
The Park Service management policy has wording specifically dedicated to preserving the soundscape. (Box 2-1 provides an overview of the NPS soundscape policy.) The policy defines the soundscape as all natural sounds occurring in parks, the capacity for transmitting those sounds, and the relationships among natural sounds. Such sounds can be transmitted through air, water, or solid material and may fall outside the range of human perception. The goal, Trevino said, is not only to preserve existing soundscapes but also to restore those that have been degraded and prevent further damage. In addition, the Park Service aims to protect culturally appropriate sounds, such as music at the New
BOX 2-1 Soundscape Management in the National Park Service
NPS Soundscape Management Policy 4.9. According to this section of the 2006 NPS Management Policies, “Using appropriate management planning, superintendents will identify what levels of human-caused sound can be accepted within the management purposes of parks…. In and adjacent to parks, the Service will monitor human activities that generate noise that adversely affects park soundscapes, including noise caused by mechanical or electronic devices. The Service will take action to prevent or minimize all noise that, through frequency, magnitude, or duration, adversely affects the natural soundscape or other park resources or values, or that exceeds levels that have been identified as being acceptable to, or appropriate for, visitor uses at the sites being monitored.” (For more information, see www.nature.nps.gov/sound/assets/docs/SoundscapeManagement_4.9.pdf.)
NPS Cultural Soundscape Management Policy 5.3.1.7. This section of the 2006 Management Policies states that “The Service will preserve soundscape resources and values of the parks to the greatest extent possible to protect opportunities for appropriate transmission of cultural and historic sounds that are fundamental components of the purposes and values for which the parks were established.” (For more information, see www.nature.nps.gov/sound/assets/docs/CulturalSoundscapeManagement_5.3.1.7.pdf.)
NPS Director’s Order #47: Soundscape Preservation and Noise Management. This order “directs park managers to (1) measure baseline acoustic conditions, (2) determine which existing or proposed human-made sounds are consistent with park purposes, (3) set acoustic management goals and objectives based on those purposes, and (4) determine which noise sources are [adversely] impacting the park and need to be addressed by management.” (For more, see www.nps.gov/policy/DOrders/DOrder47.html.)
Orleans Jazz National Historical Park and military sounds at national battlefield parks. The mandate extends to all sounds in and adjacent to the national parks, so sounds outside official boundaries are still of concern.
The NPS wilderness policy authorizes the use of motorized equipment or mechanical transport only if it is determined by the superintendent to be the minimum required to achieve the purposes of the area, including the preservation of wilderness character and values, or in emergency situations such as search and rescue, homeland security, or law enforcement. The Wilderness Act, which is distinct from legislation governing the national parks, is also concerned with soundscapes. (Box 2-2 cites some of the policies governing motorized equipment in national parks.)
Park managers are responsible for making and implementing decisions about which sounds contribute to the park and which may hinder the visitor experience. “Many park visitors have certain expectations regarding the sounds they will hear,” Trevino explained. “Natural sounds such as waves breaking on the shore, the roar of a river, and the call of the loon form a valued part of the visitor experience. Conversely, the sounds of motor vehicle traffic, an electric generator, or loud music can greatly diminish the serenity of a visit to a national memorial, the effectiveness of a park interpretive program, or the ability of a visitor to hear a bird singing its territorial song.”
NOISE GENERATED IN THE NATIONAL PARKS
Park-generated noise can be broadly divided into the three categories of transportation, facilities and maintenance, and construction discussed by the breakout groups, explained Frank Turina, program manager for policy, planning, and compliance in the NPS Natural Sounds and Night Skies Division.
The survey of park superintendents that prompted interest in holding the workshop revealed that many sources of noise in parks are associated with park operations and maintenance. Similarly, many NPS staff requests for assistance involve problems with noise. The extensive networks of bridges, trails, structures, and roads throughout the national parks require constant maintenance. Noise from buildings, such as that generated by heating, ventilation, and air conditioning (HVAC) systems, often affects the outdoor environment. Transportation by park vehicles and by vehicles supporting concessionaires generates noise. Landscaping, trail maintenance, mowing, and snow removal all contribute to noise levels. “We need to focus inwardly and take a look at the kind of noise that the parks themselves are generating, and to develop some tools and guidance for parks to help them
Wilderness Act 36 CFR Section 2.12 Audio Disturbance. Under this section the following is prohibited: Operating motorized equipment or machinery that exceeds a noise level of 60 decibels measured on the A-weighted scale at 50 feet or, if below that level, nevertheless makes noise that is unreasonable. (For more information, see www.gpo.gov/fdsys/pkg/CFR-2010-title36-vol1/pdf/CFR-2010-title36-vol1-sec2-12.pdf.)
Wilderness Act 36 CFR Section 2.18 Snowmobiles. Under this section, “Snowmobiles are prohibited except where designated and only when their use is consistent with the park’s natural, cultural, scenic and aesthetic values, safety considerations, park management objectives, and will not disturb wildlife or damage park resources.” The following are also prohibited: “Operating a snowmobile that makes excessive noise. Excessive noise for snowmobiles manufactured after July 1, 1975, is a level of total snowmobile noise that exceeds 78 decibels measured on the A-weighted scale at 50 feet.” (For more information, see www.gpo.gov/fdsys/pkg/CFR-2010-title36-vol1/pdf/CFR-2010-title36-vol1-sec2-18.pdf.)
Wilderness Act 36 CFR Section 3.15 Maximum Noise Level for Operation of Boats. A person may not operate a moving vessel at a noise level exceeding 75dB(A) measured using the test procedures in this section. (For more information, see www.gpo.gov/fdsys/pkg/CFR-2010-title36-vol1/pdf/CFR-2010-title36-vol1-sec3-15.pdf.)
NPS Policy 8.2.3 re Use of Motorized Equipment. This section of the 2006 Management Policies discusses motorized off-road vehicle use, snowmobiles, and personal watercraft use. (For more information, see www.nature.nps.gov/sound/assets/docs/MotorizedEquipment_8.2.3.pdf.)
prevent or mitigate the noise that they are creating just doing their normal day-to-day operations.”
Turina showed slides of spectrograms from acoustic monitoring equipment depicting acoustic data from several national parks. Spikes
occur when birds are singing in the morning or when helicopters fly overhead. Unexpectedly high levels can indicate sources of noise that need attention. HVAC systems in Yosemite, for example, caused high levels of noise in the middle of the night. At Mount Rushmore, maintenance personnel power washing the walkways caused a spike in noise.
In a quiet location, Turina pointed out, noises like those generated by a chainsaw can travel great distances. “We’re dealing with a different kind of situation here where we have extremely low ambient noise levels,” he said. Ambient noise levels in the national parks, measured in decibels, can be in the teens or low 20s, levels that approach the threshold of human hearing. The topography and the season also influence how far noise carries, as several workshop participants pointed out.
In discussing construction noise, Turina used as an example a breached irrigation ditch in Rocky Mountain National Park. The environmental impact statement for repairing the damage revealed that all of the construction equipment would be the same as that used in an urban setting, such as bulldozers, backhoes, and power tools. Similarly, retrofitting a fire tower in the backcountry of Glacier National Park required generators, drills, saws, grinders, and many other tools. “Providing parks with some guidance and tools for minimizing the noise that these things create is really important for us,” Turina said.
Transportation noise, he explained, is generated by any equipment used primarily for moving people or equipment. The national parks have 110 transit systems, including systems operated by park concessionaires. Vehicles and transportation systems used by park personnel were included in the scope of the workshop, as were large-capacity tourist vehicles, but not recreational and private vehicles. Spectrograms reveal extensive noise from, for example, buses in the Grand Canyon. But Turina noted that in Zion National Park, a shuttle system installed 12 years ago to clear up a congested roadway has cut in half the percentage of time that vehicles are audible in some parts of the park, which suggests possibilities for improving transportation systems in general.
A workshop participant commented on the debate about whether less noise for a longer period is preferable to more noise over a shorter period. The timing, duration, and amount of noise are all important, Turina answered. In addition, lower-frequency noise travels farther and is less subject to attenuation by vegetation and topography. Another participant observed that what people perceive can differ greatly from what they actually hear. Audibility protocols in the parks, Turina said,
are based on an algorithm that enables researchers to determine audibility in real time through various methods.
Trevino added that the metrics used by the Park Service to measure and characterize sounds are different from those used by other federal agencies because of the NPS mission to preserve natural and cultural resources. That is appropriate, said another workshop participant, because other standards are based on other factors, such as protecting human health. Also, what is unacceptable in one park might be acceptable in a different park where levels of background noise are higher.
The Park Service was planning to work with the Volpe National Transportation Systems Center after the workshop to develop tools and strategies to minimize noise, Turina concluded. But every park is unique and each will need to consider how the recommendations could fit its situation. “We’re basically at step one,” he said. “We’re headed down the road to a systemwide program and guidance to help parks make these day-to-day decisions on how to reduce noise.”
Box 2-3 lists some of the most objectionable noises in national parks cited by workshop participants.
BOX 2-3 Examples of Noise Challenges
During the opening plenary session, Trevino invited the workshop participants to list the biggest noise challenges they have encountered in the national parks. They mentioned the following:
- Construction noises
- Overflights by helicopters and fixed-wing aircraft
- Other kinds of flights (e.g., search and rescue, maintenance)
- Vehicles, especially low-frequency noises from buses and trains and the distant “drone” of highway traffic
- Backup alarms on vehicles
- Motorcycles, especially those with modified exhaust systems
- Personal watercraft, snowmobiles, and airboats
- Lawn care equipment
- Generators, chainsaws, and other types of equipment
- Human-generated noise
Population growth, said Kurt Fristrup, senior scientist in the Natural Sounds and Night Skies Division, is projected to affect ambient noise levels. Population density is growing near the parks, and transportation noise is growing even faster than population. Data from the Department of Transportation show that over a period of time when population increased by 30 percent, sources of road and aircraft noise doubled and even tripled in some areas. In most areas of the United States, over half of all watersheds are within 380 meters of a road, making road traffic a common source of noise pollution nationwide. New natural gas exploration technologies will also bring noise to many previously quiet areas.
Decades of research show that animal diversity and density tend to decrease near roadways, with the exception of a few (usually) invasive or exotic species. The dearth of wildlife near roadways could be due to factors other than roadway noise, but increasing evidence points to the importance of noise. For example, studies looking at energy exploration have found that noise has a significant impact on breeding birds—male sage grouse abandon areas where energy exploration creates noise.
It is not clear whether animals interpret the noise as a threat or are simply reacting to the environmental degradation caused by noise. One experiment with collared elk found that they would move away from the sound of vehicles up to a kilometer away, but they were more likely to move when they were on a trail or road than if they were off the trail, which suggests that they were reacting to a perceived threat rather than the irritation of the noise. Mountain goats react to the sound of helicopters, which are often used in tagging the goats for wildlife research. Humpback whales show changes in their singing and interaction behaviors for up to three hours after a sonar event, and aircraft flying at low altitudes can disrupt behavior in ducks and other species for up to two hours afterward.
Research has largely focused on the aversive reactions of wildlife to very loud noises. But chronic noise is also an issue, and Fristrup has advocated for research into the ecology around roadways to determine what the impact might be. Some animals have hearing thresholds at or below the quietest measured levels, and increases in chronic noise of just a few decibels could have a significant adverse effect.
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1 For an annotated bibliography of research on the impacts of noise on wildlife, see www.nature.nps.gov/sound/assets/docs/Wildlife_AnnotatedBiblio_Aug2011.pdf.
Some animals rely on sound when hunting prey, while others listen for warnings. The animals that rely most heavily on sound are probably more affected than others by increased noise, Fristrup said; predators generally have the most sensitive hearing among animals, enabling them to search the widest area. Owls have hearing sensitivity that is as much as 20 decibels better than humans, as do some bats. (One challenge in the field has been to develop microphones that can hear as well as some animals.)
Animals use sound for purposes other than hunting. For example, migrating birds listen to sounds coming from the ground to decide where to stop, and many species of amphibians listen to wildlife calls to decide which ponds are suitable for breeding.
Some animals may become habituated to noise, but that does not mean that it does not have an impact. Noise can change the breeding success of animals, both in the field and in the laboratory, or cause animals to miss a class of events that are important for them. Also, an animal subjected to a chronic stressor and then exposed to a second stressor may experience a more acute stress response than it would without the chronic stressor. This is an important area for additional research, Fristrup said, particularly as ambient noise levels increase.
In response to a question, Fristrup noted that endangered species are treated the same as other species in considering the effects of noise, but the biology of each species must be taken into account. Tortoises, for example, may respond more to ground-borne vibration than to noise itself.
EFFECTS OF NOISE ON PARK VISITORS2
Researchers have looked at the effects of noise on the people who visit national parks, Fristrup continued. Surveys of park visitors show that soundscapes are important to them, and research has found that scenery is more meaningful to people when there is less artificial noise. Lower noise levels also help visitors hear wildlife such as wolves, which are more likely to be heard than seen.
Survey data further indicate that visitors are willing to help keep park areas quiet. At Muir Woods National Monument, for example, visitors observe quiet zones and quiet days when requested by posted signs (though they expressed more support for the quiet zone concept).
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2 For an annotated bibliography of research on the impacts of noise on visitors and soundscapes, see www.nature.nps.gov/sound/assets/docs/VisitorExperience_Soundscapes_AnnotatedBiblio_17Aug10.pdf.
On posted quiet days, visitors were significantly quieter than on other days. A “lost listening area” is an effective way to talk about a noise problem without mentioning decibels, Fristrup said, since many people do not have a good grasp of what decibels mean. (Overnight visitors also expressed concern about sleep interference, he said, but this issue has not been studied in parks.)
Fristrup discussed the necessity of finding an appropriate metric when conducting noise research. The most commonly employed metrics use A-frequency weighting—a standard weighting curve that makes the metric generally representative of human hearing. But for some measurements, sampling should be limited to the frequencies most often produced by a particular source. In other cases, animals may have hearing sensitivities that differ from those of humans. As a workshop participant pointed out, whales have better low-frequency hearing than humans. In those cases, said Fristrup, using a human model may be inadvisable. However, humans have better low-frequency hearing than most other vertebrates, so an A-weighting curve is generally a conservative measurement. “[Human] hearing has also been extremely well studied,” he said. “Someone with healthy hearing can go out in the field and make observations that mean something.”
Researchers sometimes measure the average noise level generated by a given source, but it is difficult to relate this measure to everyday experiences for the public. Knowing how often a noise is present and how loud it is helps with public education. A perceived loudness standard also may be preferable for higher noise levels.
The question of noise metrics was also addressed by George Maling in his brief review of the Technology for a Quieter America report (NAE 2010). Citing the NAE report, Maling noted that human reactions to man-made and natural sounds differ, and that a different metric may be required for the assessment of noise impacts on wildlife. He also observed that the metric used to assess environmental noise depends on the source; for example, aircraft noise is assessed differently from highway noise. For the types of sources discussed at the workshop, the noise metrics will differ but have generally been defined for various noise sources.
Beth Cooper, an acoustical engineer and hearing conservation consultant with the National Aeronautics and Space Administration (NASA),
described the agency’s Buy-Quiet program3 to help the NPS explore possible applications to the national parks. NASA has a hierarchy of concerns in managing noise, from low-level noise to levels that can cause hearing loss, with issues such as community noise, communication intelligibility, and productivity falling somewhere in between. Many outside factors also influence the management of noise, including federal regulations,4 local ordinances, best practices guidance,5 and industry standards, as well as voluntary policies6 that a company may choose to adopt.
Minimizing Noise Generation and Exposure
The first priority, Cooper said, is eliminating noise that is hazardous to human hearing. Engineering controls are preferred over administrative controls or personal protective equipment, which should be the last resort. Buy-Quiet falls into the engineering realm, encompassing low-noise design, noise emission specifications for purchased equipment, and retrofit solutions for existing systems.
The NASA Buy-Quiet program grew in part from efforts to control noise on the International Space Station. Every module on the space station houses noise-emitting equipment, which generates enough noise to interfere with communication. Poor communication impacts safety and data accuracy and can threaten the success of a mission. Addressing communication problems generally covers hearing loss prevention goals as well, Cooper pointed out.
NASA assigned emission noise level targets for each module, and a noise emission target was suballocated to each piece of equipment in the module, based on an overall noise emission budget. Payload developers were asked to comply with those levels. Although many waivers were granted early in the process, Cooper said, with sustained efforts the number of compliant payloads increased substantially over time.
From 1999 to 2007, Cooper managed the NASA Glenn Research Center Acoustical Testing Laboratory,7 which offered low-noise design
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3 For more information on the Buy-Quiet program, see http://buyquietroadmap.com/buy-quiet-purchasing/.
4 See www.gpo.gov/fdsys/pkg/CFR-2011-title29-vol5/xml/CFR-2011-title29-vol5-sec1910-95.xml.
5 See www.cdc.gov/niosh/docs/98-126/pdfs/98-126.pdf.
6 See http://buyquietroadmap.com/buy-quiet-purchasing/buy-quiet-program-requirements/.
7 For more information on the Acoustical Testing Laboratory, see http://buyquietroadmap.com/wp-content/uploads/2010/01/NASA_ATL_Five_Year_Retrospective.pdf.
services for payload developers. The laboratory tested purchased sound sources individually and then built them into larger systems, using noise modeling to predict the noise emission output of the complete system. The noise emission of each payload and system had to be test-verified in the anechoic chamber prior to launch. When systems do not meet noise emission standards, they have to be retrofitted for noise control, often in-orbit, which is expensive and time consuming.
For ground-based noise exposure, she continued, NASA’s program is similar to those of many companies in the private sector, where the primary motivation is prevention of noise-induced hearing loss. Managing occupational noise exposure requires a multidisciplinary program that includes noise exposure monitoring, noise control engineering, and audiometric monitoring, to name just a few elements. The NASA program maintains requirements that are more stringent than those of the Occupational Safety and Health Administration (OSHA): NASA has adopted the “85/3” criterion,8 which consists of a maximum noise exposure limit of 85 decibels (dB) using A-frequency weighting averaged over an 8-hour workday, using a 3 dB exchange rate. Anyone exposed to noise above 85 dBA is required to wear personal protective equipment. Every three years, internal NASA site audits check for policy compliance. Many professional associations, including the National Hearing Conservation Association,9 have been promoting similar standards for many years because OSHA’s more liberal noise emission limit of 90 dBA time-weighted average (TWA), using a 5 dB exchange rate, is not considered to be very protective, according to Cooper.
Creating a low-noise workplace goes a step beyond providing personal hearing protection. Reducing noise greatly lowers the risk of hearing loss and the costs associated with noise, including the costs of maintaining a hearing conservation program and of hearing loss claims, in addition to improving communication and concentration by developing a more productive and comfortable work environment (Nelson 2012).
The NASA Buy-Quiet program and its newer sister program Quiet by Design are built around controlling noise emission rather than worker exposure to noise, Cooper explained (Cooper 2010). The purchaser issues a noise specification and the manufacturer is responsible for designing equipment to meet the specification. The standards are subject
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8 For more information, see www.hearingconservation.org/displaycommon.cfm?an=1&subarticlenbr=142.
9 Online at www.hearingconservation.org/index.cfm.
to what is achievable; for example, it can be difficult to impose stringent requirements for off-the-shelf products. Also, certain government procurement processes that limit the amount of controls the purchaser can attach may introduce more noise emission risk into the procurement. “In that case, you would select a procurement vehicle that allows an appropriate degree of noise emission risk,” she said.
Low-noise equipment may be more expensive at the purchase point, but it is usually preferable to retrofitting, which is expensive and sometimes nearly impossible. As a rule of thumb, retrofitting engineering controls can cost 10 to 15 times more than the premium for low-noise equipment. Low noise also means better engineering. “Noise is a waste byproduct,” Cooper said. “It’s inefficient, it’s unwanted, it’s a waste of money and energy, and it introduces harmful vibration for people and equipment. It can also impact science data acquired in the presence of the vibration.” In addition, Workers Compensation and medical and psychological impacts contribute to the expense of managing the effects of noisy equipment. Getting people to think about the long-term costs of noise is part of the advocacy process, she said, and determining those long-term costs will be part of the challenge for the Park Service.
A formalized procurement process is important because it communicates the seriousness of the goal. At NASA a Buy-Quiet requirement was added to agencywide procedures10 in 2006, with responsibility for site-specific implementations distributed in every NASA field center. Because the technical component of the program is outside most employees’ experience, advocacy and training are part of successful implementation. Each field center has a Buy-Quiet Program Lead in the environmental health/safety organization, and coordination and coaching throughout NASA are provided by a subject matter expert (Cooper) under the auspices of NASA’s Office of the Chief Health and Medical Officer. Triennial audits of each center by a headquarters team provide periodic program reviews and identify opportunities for improvement, which are the responsibility of the center’s management. Eventually, the supply of quiet products offered by manufacturers will increase to match the demand; public, official, and formal procedures fuel this process and also increase the likelihood that a program will succeed and influence the creation of others.
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10 Online at http://nodis3.gsfc.nasa.gov/displayDir.cfm?Internal_ID=N_PR_1800_001C_&page_name=Chapter4.
Purchasing versus Retrofitting
The first step in a Buy-Quiet procurement process, Cooper explained, is planning the procurement. This means knowing the functional requirements for the object being purchased and the in situ noise-emission requirements. In NASA’s web-based Buy-Quiet Roadmap tool,11 the default procurement process requires formal comparison of products, considering the differences in both noise emission and cost. It also uses a procedure to calculate the cost of noise in order to estimate the net present value of long-term exposure to the noise generated by each product. This calculation enables the contracting officer to weigh the purchase price against the long-term cost associated with the product. This calculation would need to be customized for parks, for which lower-level noise is also problematic and for reasons other than hearing loss risk, Cooper acknowledged, but it could certainly be adapted.
Establishing baseline noise emission criteria is an important part of the process. Cooper cited the European Union (EU) machinery directive,12 based on best practices and what is technically achievable, as a good resource. If the product doesn’t appear there, 80 dBA sound level at one meter is NASA’s default assumption. Sometimes, an informed adjustment of the noise emission criterion is necessary. If equipment is sited outside, NASA uses a community noise checklist,13 which alerts the purchaser to any potential problems.
The more risk there is, Cooper said, the more complex the procurement process. Targeting procurement strategy for each purchase allows the maximum use of simpler procurement vehicles. If the purchase must go through the complete tradeoff process, a tradeoff analysis worksheet can be used to evaluate the net long-term cost of candidate products, enabling the contracting officer to make a selection based on all the relevant information. Using the worksheet to record the noise-level criterion, the number of employees exposed, the quoted sound power level for each item, and environmental characteristics, it is possible to compute the net cost of additional noise for up to three products at a time.
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11 For more information, see http://buyquietroadmap.com/buy-quiet-purchasing/buy-quiet-process-roadmap/.
12 For more information, see http://ec.europa.eu/enterprise/sectors/mechanical/documents/legislation/machinery/index_en.htm.
13 For more information, see http://buyquietroadmap.com/buy-quiet-purchasing/buy-quiet-process-roadmap/forms-worksheets/community-noise-check/.
There are two forms of noise emission verification, one performed at the manufacturer’s shop before shipment and one performed in the field after installation. NASA field centers have the autonomy to waive either test and to accept a product that fails one or both tests, but a higher level of management authorization is required in order to do so. “We’re trying to provide a process with informed and responsible decision making but not tie anyone’s hands,” Cooper explained.
Adapting the Buy-Quiet Program
Although the Buy-Quiet program was designed to meet NASA’s needs, it is applicable to private industry and to other government programs. Two versions of NASA’s cost-of-noise model are online, one intended for general Buy-Quiet program advocacy uses and a simplified version for comparing candidate items. The Buy-Quiet Roadmap links to many other resources, such as cost-benefit analyses done by the Navy and other hearing loss calculators. Related resources, such as papers from NASA and presentations on the Buy-Quiet program, are available for download. Hyperlinks direct users to forms and other tools.
The National Institute for Occupational Safety and Health (NIOSH) has adapted elements of NASA’s Buy-Quiet program for the construction industry using a three-tiered approach. Companies can authorize the lowest-noise purchase independent of cost, decide to purchase nothing louder than what already exists, or purchase on a decibel-per-dollar range decided by the manager. Another common approach, sometimes used by municipalities to manage construction-associated noise, is to prequalify a list of equipment that meets a predetermined noise emission goal (Thalheimer 2011). Finally, companies buying major pieces of expensive custom-designed equipment may collaborate with the manufacturer to meet stringent requirements. The bottom line, Cooper said, is that programs differ based on operations, culture, size, and the number and diversity of purchases as well as the number of potential vendors.
Cooper pointed out that not all aspects of the NASA Buy-Quiet program may be relevant for Park Service purposes. “When it comes to noise in parks, we first need to be able to find a way to quantify the value of the visitor experience and the value of the impact on wildlife. That’s still the fundamental challenge—to quantify the cost of noise.”
LOW-NOISE PRODUCTS IN THE NATIONAL PARKS
Randy Stanley, an acoustic specialist for the National Park Service, concluded the plenary session by briefly discussing some NPS steps to procure low-noise products. The complication for the national parks is that the natural ambient sound level is the baseline against which impacts will be evaluated, but ambient levels vary greatly from one park to the next. Superintendents at each park are responsible for identifying what levels of noise constitute acceptable impacts, but they, too, face the problem of defining what is acceptable. One park may need to accommodate battlefield sounds, while at another even a single automobile may be inappropriate.
In 2008 the Park Service began putting together information on how to reduce noise through low-noise products, using data from a Noise Pollution Clearinghouse (www.nonoise.org), the Consumers Union, and other sources. In 2009 an NPS guidance pamphlet was circulated to all the parks, with plans for updating over time (NPS 2011). The guidance recognizes that purchasers consider a wide variety of information when making decisions, including ease of use, power, flow rate, efficiency, weight, and engine design. At Glacier National Park, for example, large amounts of snow need to be removed from roadways each year, requiring the use of heavy equipment. And the lightweight chainsaws used by the Park Service (because they need to be carried long distances into the backcountry) are often noisier than others. Given such considerations, the pamphlet provides information on various strategies for making low-noise purchases.
