Understanding Environmental Sound: Definition, Impact, and Solutions

Environmental sounds play a crucial role in our daily lives. They surround us, influence our mood, and often affect our productivity. From the soothing rustle of leaves to the incessant honking of urban traffic, these sounds shape our experiences. Understanding environmental sounds can help enhance our focus and improve our overall well-being.

From the moment of birth we are literally and figuratively immersed in a sea of sounds. We quickly learn that sound is essential for us to communicate with one another, to enjoy drama and musical performances, as well as recorded symphonies, jazz or rock music, and to appreciate countless other sounds we want to hear.

But some sounds around us may interfere with our ability to communicate. They may mask our enjoyment of desirable sounds; they may interfere with our ability to concentrate on a task or to learn a new one. Other sounds may startle us, interrupt our sleep, cause us psychological stress, contribute to physiological distress and, when sustained and loud enough, contribute to temporary or permanent loss of hearing. These latter sounds are "unwanted" and, by definition, are considered noise.

Defining Environmental Sounds

Environmental sounds refer to the various noises present in our surroundings, both natural and artificial. They can be categorized into three main types: natural sounds, artificial sounds, and ambient sounds.

• Natural sounds: These sounds can include water flowing in a stream or river, wind rustling through trees, and wildlife sounds, like birds singing or frogs croaking.
• Artificial sounds: Common examples are traffic noise from cars, buses, and trains, human activities, such as talking or construction work, and mechanical sounds from appliances or machinery.
• Ambient sounds: This encompasses all background noise in an environment, blending both natural and artificial sounds.

Recognizing these types of sounds can help us appreciate their significance in our surroundings.

Environmental Sounds for Relaxation and Focus

Environmental Noise: A Deeper Dive

According to the World Health Organisation (WHO) definition, environmental noise is noise emitted by all sources within an environment, other than noise generated in the workplace. Sometimes, such noise can affect concentration (which can have a serious impact on workplace productivity and academic learning) and may even cause health problems.

Environmental noise in and around buildings and communities in which people live and work has gradually and steadily increased in magnitude and diversity as civilization has advanced. The industrial growth and introduction of railroads in the 19th century accelerated the pervasiveness of environmental noise. In the 20th century, industrial growth even more dramatically exposed larger and larger segments of the population to noise, especially from the new mode of transportation-aircraft. In particular, the introduction of jet aircraft into the civil fleet in the late 1950s and early 1960s spurred the scientific- technical community, as well as the political leader-ship, to look for solutions to the growing problem of aircraft noise and environmental noise in general.

Protecting the health of the population is and continues to be the primary motive of all public efforts to control individual and community exposure to noise. The United States has adopted the World Health Organization's (WHO) broad definition of health as not the mere absence of disease, but as the total physiological and psychological well-being of the citizenry. Congress enacted the Environmental Protection Act of 1969 and the Noise Control Act of 1972 to mandate and implement practical and achievable standards and policies to ensure that the broad public health and environmental objectives with respect to individual and community noise are met. The United States Environmental Protection Agency (EPA), which grew out of the 1969 environ-mental legislation, assumed responsibility for coordinating the development of noise policies, standards, and guidelines in cooperation with several major federal agencies.

Chief among them are the Federal Aviation Administration (FAA), the Federal Highway Administration (FHWA), the Department Of Housing and Urban Development (HUD), and others having cognizance over major sources or receptors of environmental noise.

The steadily growing concern for and adoption of means to control environmental noise are everywhere evident. The proliferation of highway noise barrier walls along the nation's interstates and major thoroughfares is but one visible manifestation of the success of this landmark environmental legislation of decades ago. Hundreds of residential communities near these major transportation routes are significantly quieter because of these noise abatement measures. Highway engineers and architects are even developing noise barrier walls and landscaped berms that are aesthetically pleasing to both motorists traveling the highways and the residents on the other side of these barriers. The fact that the noise output of the larger and more powerful jet engines necessary to serve the nation's insatiable demand for air travel has not increased with the increased mechanical power of the jet engines themselves is evidence that the nation's efforts to control noise have been productive. In fact, aircraft noise exposure in communities around airports has for the last ten years been on the decrease, as quieter aircraft become more prevalent, even though air traffic has been on the increase.

This article reviews environmental noise descriptors and policy guidelines for abating environ-mental noise on which the scientific-technical community, governmental agencies, industry and consumer-public interest groups generally agree. Likewise those planners, architects, engineers and all involved in the design, specification, and construction of "built" environments need these noise guidelines and standards in order that they may provide effective controls of environmental noise when they are needed. Over the past several decades, standards and guidelines have been quite successfully applied on federally funded airport, highway, transit, and housing projects. More importantly, these standards and guidelines have served as a basis for enactment of standards and guidelines by state and local agencies throughout the country.

Principal Descriptors for Evaluating Environmental Sound

The principal descriptors for evaluating environmental sound are enumerated in Table 1 and discussed further below.

A-Weighted Sound Levels

The full, audible frequency range for young, healthy ears extends from about 20 Hz (cycles per second) to about 20,000 Hz. However, the human hearing mechanism is most sensitive to sounds in the 500- to 8,000-Hz range. Above and below this range, the ear is inherently less sensitive. With increasing age, the ear becomes progressively less sensitive to sound over the entire frequency range (presbycusis). Persons who are exposed to loud noise over a long period of time can also incur a hearing loss that usually most significantly affects hearing acuity in the mid- and high-frequency ranges. To account for the varying sensitivity of the normal human ear to sound over the audible frequency range, sound level meters incorporate an electronic filter (or weighting network) that approximates the way the human ear perceives sound over the audible frequency range. Sound level values obtained using this weighting network are referred to as "A-weighted" sound levels and are signified by the identifying unit, dBA. Another important feature of the human hearing mechanism is its ability to process sound over a tremendous dynamic range from the threshold of audibility to the threshold of pain, which is a million times as intense as sound at the threshold of hearing.

An increase or decrease of 10 dBA is perceived as a doubling or halving of loudness. For example, selecting 60 dBA as a reference level, a sound level of 70 dBA would appear to be twice as loud.

Time-Varying Sound Levels

Both indoor and outdoor environmental sound levels usually vary markedly with time, whether in a relatively quiet setting such as in a remote rural area or in highly developed downtown urban community.

Often, the "noise floor" or background sound of an area is expressed as the sound level exceeded 90 percent of the time, symbolized as the L90.

The one percentile sound level, L1, is generally taken to be representative of typically intrusive, high sound levels observed during a time interval.

Clearly, most outdoor sound is best described in statistical terms in order to account for its time-varying character. Indeed, many community noise ordinances written only in terms of simple, unqualified limit values are not only difficult to evaluate, but encourage situations where the limits are unenforceable and largely ignored.

Energy-Equivalent Sound Levels

The recent availability of inexpensive, yet sophisticated, sound level meters, as well as the adoption of improved standards and guidelines by federal and local agencies, has fostered the use of sound level descriptors that accommodate the time-varying character of environmental noise. Chief among these descriptors is the energy-equivalent sound level (Leq). The Leq is the hypothetical steady-state sound level that contains the same amount of acoustical energy as the actual time-varying sound over a specified time interval.

Environmental Noise from the Grand Canyon to the Freeways of Los Angeles

An EPA study in 1971 produced an extremely valuable database of environmental sound at some eighteen locations throughout the United States. The quietest location measured was at the north rim of the Grand Canyon where background sound levels (L90) were about 15 dBA. Even the sound level exceeded 50 percent of the time (L50), sometimes referred to as the "time average" level, was as low as 20 dBA. Note however, that due to occasional sight-seeing aircraft flyovers, the level exceeded one percent of the time (L1) reached 47 dBA, some 32 dBA above the background or generally quietest levels. This indicates the usefulness of percentile sound levels for describing environmental noise.

Consultants in acoustics make extensive use of percentile sound levels as they give a comprehensive picture of how sound varies in the environment. The usefulness of percentile sound levels is becoming more widely recognized. National Park Service has become acutely aware of the noise resulting from excessive park development and from recreational vehicles and aircraft overflights. Policies and procedures are under development and are being implemented by the National Park Service to address these growing threats from environmental noise to the serenity of our national parks.

Figure 3 also shows the other extreme as well, a very noisy location on the third floor balcony of an apartment overlooking a heavily traveled multi-lane freeway. Think of it: persons on this balcony would need to converse with raised voices at a distance of about two feet in order to be understood over the continuous din of traffic sound.

Figure 3 also demonstrates that typical back-ground sound levels (L90) rarely fall below about 40 dBA, even for relatively quiet rural-suburban locations. Background sound levels (L90) increase to the 45 to 50 dBA range in more densely populated urban locations that are not too close to major highways or airports. Figure 3 also indicates that intermittent, intrusive noise levels (L1) are typically set by aircraft overflights near airports and by trucks near highways.

It is quite likely that environmental sound conditions for almost all of South Carolina's cities and towns could be characterized, without the benefit of a detailed acoustical measurement survey, simply by matching descriptions of these cities and towns with descriptions of the eighteen locations of Figure 3.

It may be also observed from the statistical noise data of Figure 3 that the time average, L50, sound levels are typically well below the L10 levels at nearly all eighteen locations. The gap is generally larger, on the order of 15 dBA, in quieter locations and in locations near airports. Based on examination of large sample of highway noise data, the FHWA has determined that the Leq value for traffic noise is typically 3 dBA below the L10 value. Accordingly, the current FHWA standard allows the use of either Leq or L10 in highway noise analyses and design of abatement measures, but not both an any single project (see Table 2 following).

Day/Night Average Equivalent Sound Levels

Noise levels occurring at night generally produce greater annoyance than do the same levels occurring during the day. It is generally agreed that people perceive intrusive noise at night as being 10 dBA louder than the same level of intrusive noise during the day, at least in terms of its potential for causing community annoyance. This increased sensitivity to sound at night has been incorporated into the day-night average sound level, which is symbolized as the Ldn, to account for increased community sensitivity to nighttime noise.

Because of their sensitivity to frequency and temporal characteristics of noise, both the Leq and the Ldn have become widely used in environmental noise regulations and criteria.

HUD Standards

HUD is the lead federal agency setting standards for interior and exterior noise for federally supported housing. The standards, outlined in 24 CFR part 51, establish Site Acceptability Standards based on day-night equivalent sound levels. In Table 2, ranges of Ldn values are correlated with various dispositions of HUD acceptability categories for housing and associated need for noise abatement, either at the site property line or in the construction of the building exterior envelope. These have been devised to achieve the HUD goal for interior noise levels not exceeding an Ldn of 45 dB.

• "Acceptable" sites are those where noise levels do not exceed an Ldn of 65 dB. Buildings on acceptable sites do not require additional noise attenuation other than that provided in customary building techniques.
• "Normally unacceptable" sites are those where the Ldn is above 65 dB but does not exceed 75 dB. Housing on normally unacceptable sites requires some means of noise abatement, either at the property line or in the building exterior, to ensure that interior noise levels are acceptable. From a practical stand-point, this requirement usually means that buildings must be air-conditioned so that windows can be closed to reduce exterior sound transmission into interior spaces.
• "Unacceptable" sites are those where the Ldn is 75 dB or higher. The term "unacceptable" does not necessarily mean that housing cannot be built on these sites, but rather that more sophisticated sound attenuation would likely be needed, and that there must exist some benefits that outweigh the disadvantages caused by high noise levels. Most often, housing on unacceptable sites requires high sound transmission loss (TL) glazing and air conditioning so that windows can be kept closed to obtain the full building envelope noise reduction.

The Impact of Environmental Sounds on Productivity

The sounds we encounter daily can significantly influence our productivity. Research indicates that specific sounds can enhance focus, while others may hinder our ability to concentrate.

Positive Effects of Environmental Sounds

Certain environmental sounds, particularly natural sounds, have been shown to improve concentration and reduce stress. For instance, studies suggest that listening to nature sounds can elevate mood and foster a more productive atmosphere. White noise and soft ambient music are also effective in masking distracting sounds and enhancing focus.

According to a study published on how ambient sounds affect focus, incorporating pleasant sounds in our workspace can significantly boost our efficiency.

Negative Effects of Environmental Sounds

Conversely, excessive noise can lead to distractions and reduced productivity. Loud urban noise, such as construction or traffic, can disrupt thoughts and hinder performance. A study found that exposure to high noise levels can negatively affect work performance, ultimately leading to decreased focus and increased stress levels.

Environmental Sounds and Mental Well-being

Environmental sounds also have a profound impact on our mental health. They can either alleviate stress or contribute to anxiety, depending on the nature of the sounds.

Therapeutic Uses of Environmental Sounds

Nature sounds have been used in therapy and mindfulness practices to enhance relaxation and promote a sense of well-being. Listening to sounds like ocean waves or birdsong can lower stress hormones and create a calming environment. Research has shown that nature sounds can help heal not just the mind but also the body, making them effective tools in stress management.

Creating a Sound Environment for Well-being

To curate an optimal sound environment, consider integrating natural sounds into your personal and workspaces. Here are a few tips:

• Use Sound Machines: These devices can replicate nature sounds, providing a soothing backdrop.
• Play Relaxing Music: Soft instrumental music can create a calming atmosphere.
• Limit Disruptive Sounds: Use earplugs or noise-canceling headphones in noisy environments to maintain focus.

Incorporating Environmental Sounds into Daily Routines

There are practical ways to weave beneficial environmental sounds into your daily life, boosting both productivity and well-being.

Playlist Recommendations for Environmental Sounds

Creating playlists with nature sounds or soft ambient music can transform your working or studying environment. Some great options include:

• Nature Sounds: Ocean waves, rain falling, or forest sounds
• Ambient Music: Soft piano melodies or gentle electronic soundscapes

Using platforms like Spotify, you can find curated playlists focused on enhancing concentration and relaxation.

Using Technology to Create Ideal Soundscapes

In today’s digital age, technology offers various apps and gadgets designed to help create customized sound environments. Apps like “Noisli” or “Calm” allow users to mix different sounds, like rain and wind, to create their perfect soundscape.

Environmental Noise Assessment

An environmental noise assessment aims to identify, measure and analyse sources of environmental noise in order to make recommendations with regard to regulatory compliance and the comfort of workers and residents. The first and most important step is to identify the sources of environmental noise and to understand the regulations and standards applicable to the location under assessment. Indeed, some regulations quote noise levels according to the time of day.

At the next stage, the experts go into the field with their acoustic equipment in order to take the necessary sound measurements specified in the appropriate official regulations. Once the acoustical data and audio recordings have been captured and collected, the analysis can begin. A sound map of the region or location which is the focus of the assessment is created using acoustic modelling software. With the help of this zoning information, the field data, and their theoretical and practical knowledge, acoustic experts are then able to make recommendations to clients, to design equipment and materials adapted to their needs, and to assist with monitoring and any further action.

Noise Exposure Limits and Worker Safety

The strength of ambient noise levels in a given environment can have significant health and safety implications. In the United States, workers are protected from exposure to damaging levels of ambient noise by OSHA’s noise exposure limits. Other occupational safety agencies, such as the Federal Railroad Administration, also prescribe noise exposure standards. Exposure to high noise levels, especially for a prolonged period of time, can result in gradual hearing loss. Studies have also linked high noise levels to increased rates of workplace incidents.

This is partly due to impaired concentration, increased fatigue, and other symptoms interfering with the employees’ ability to work safely and recognize hazards in the work environment. Workers in noisy environments should be equipped with adequate hearing protection in the form of earplugs or earmuffs. Hearing protection can introduce new hazards, however. The less a worker is able to hear the sounds around them, the more likely they are to miss crucial information and signals about potential hazards and dangers in their immediate environment.

Environmentally Sound Technologies (ESTs)

Rational environmental management means making the best use of resources to meet basic human needs without destroying the sustaining and regenerative capacity of natural systems. Environmentally Sound Technologies (ESTs) are technologies that have the potential for significantly improved environmental performance relative to other technologies. ESTs protect the environment, are less polluting, use resources in a sustainable manner, recycle more of their wastes and products, and handle all residual wastes in a more environmentally acceptable way than the technologies for which they are substitutes. ESTs are not just individual technologies.

Technology plays an important role to improve efficiency of resources (materials and energy), reduce pollution and waste from different sectors, and manage pollution and waste that is generated during extraction of resources and production and consumption of goods and services. The importance of Environmentally Sound Technology was first emphasized during Rio Earth Summit in 1992 and ever since it has become a major component of international environmental cooperation. Access to technology also plays a central role in the groundbreaking agreement, the Addis Ababa Action Agenda – which is an implementing mechanism for the global Sustainable Development Goals (2030 Agenda for Sustainable Development).

The agreement was reached by the 193 UN Member States. Our global interdependence and vulnerability has never been more pronounced. What happens on one part of the planet will have some kind of effect, at some time, on all other parts. Global change is a dynamic process that can only be understood from a holistic and ecological perspective. In describing the interactions of parts within the global ecosystem, the Brundtland Report refers to “a complex and interlinked ecosystem”, and the need to take into account “the system-wide effects of exploitation”. Emerging from this is the rationale for sustainable development and the importance of meeting the needs of the present without compromising the ability of future generations to meet their own needs.

UN Environment is promoting environmentally sound technology in line with international agreements. A strong science-policy interface is established by UN Environment. Multi-stakeholder partnerships are supported to accelerate and consolidate the change in consumption and production patterns.