When is soundscape

Although most organisms cannot actively control which sound signals they receive, selection pressures can adjust the configuration of their auditory organs to optimize their ability to detect conspecific signals Dooling et al.

A multisource model is illustrated in figure 3b. Note that sounds from birds and amphibians may be interfered with by wind, rushing water, or potentially noise created by humans Ryan and Brenowitz The integration of all these signals, natural and human, makes up the soundscape.

Note also that an acoustic sensor array could be employed to record sounds at multiple locations; sound waves could then be conceptualized as an acoustic field that changes with time. Relevant ecological hypotheses. Two complementary hypotheses, the morphological adaptation hypothesis MAH and the acoustic adaptation hypothesis AAH , describe how ecological feedback mechanisms give rise to changes in animal signals, whereas the acoustic niche hypothesis ANH describes how these feedback mechanisms lead to the complex arrangement of signals in the soundscape.

The MAH focuses on the sender, and posits that an organism's physical attributes, such as its body size, the length of its trachea, and the structure of its beak, influence what sorts of sound signals an organism can produce e. A larger bird with a longer trachea, such as a heron or a goose, will usually produce sounds at lower frequencies than a smaller bird with a shorter trachea, such as a thrush or a finch.

The AAH e. Support for the AAH has been mixed; some researchers found no correlation between signal composition and habitat Daniel and Blumstein , whereas others e. In his formulation of the ANH, Krause pointed out that both the morphological and the behavioral adaptations described by the MAH and the AAH can also be triggered by interspecific interference when organisms' calls contain similar frequency and timing features. After repeatedly observing complex arrangements of nonoverlapping signals in his recordings of soundscapes in multiple habitat types, Krause postulated that such interspecific competition for auditory space would prompt organisms to adjust their signals to exploit vacant niches in the auditory spectrum to minimize spectral or temporal overlaps in interspecific vocalizations.

Ficken and colleagues , for instance, observed that least flycatchers Empidonax minimus at Lake Itasca, Minnesota, would insert their shorter songs between the longer songs of red-eyed vireos Vireo olivaceus when the two species shared the same habitat. An important prediction that follows from this hypothesis is that less-disturbed habitats with unaltered species assemblages will exhibit higher levels of coordination between interspecific vocalizations than more heavily disturbed habitats, in which species assemblages were recently altered.

Likewise, invasive species could create biophonic disturbances, thereby altering natural acoustic partitioning figure 4 , sound files 2—4;. Finally, Farina and Belgrano's eco-field hypothesis can be used to describe the soundscape from the receiver's perspective as a carrier of meaning.

This hypothesis proposes that an organism uses the signs it identifies in the soundscape to construct a cognitive template that it then uses to match particular spatial configurations with life functions such as food, water, and shelter.

Spectrograms of two endemic birds, Turdus merula a and Sylvia atricapilla b , and the nonendemic, invasive Leiothrix lutea c. Note that L.

Sylvia atricapilla sings at higher frequencies that are potentially masked by L. Leiothrix lutea has more behavioral overlap with S. What produces sound? The urban environment generally contains sounds with considerably different spectral and temporal properties from those produced by living organisms.

Urban landscapes are saturated with signals that carry little or no intentional information and are regarded as unwanted noise by many people. These signals emanate from vehicles e. Most of these sounds occur at low acoustic frequencies less than 4 kHz.

The geophysical environment produces a variety of in situ , contextual ambient sounds. Familiar such sounds are wind, rain, and running water, the frequencies of which occur between Hz and 1 kHz with little rain, or between Hz to 8 kHz during windy or moderate to heavy rain. Geophony varies seasonally and diurnally. Among terrestrial organisms, vertebrates and certain groups of insects produce the most sound. The most audible insects are crickets, katydids, grasshoppers, and cicadas. Insects produce sounds most strongly around 3 to 4 kHz and 6 to 8 kHz, either through stridulation crickets and katydids or by vibrating a rigid membrane cicadas.

Stridulation is created by insects by rubbing body parts together. Insects call during the day cicadas , at night crickets , or both some cicadas. Additionally, songs from many insects possess a certain periodicity.

For example, sounds from crickets are composed of pulses and chirps produced at precise intervals, and crickets are well known for having chirp rates that are strongly influenced by temperature Walker Other cyclical patterns of sound production in insects throughout the year relate to the phenological life cycle of the species.

Annual cicadas Tibicen spp. Sounds produced from wing beats from flies, bees, and wasps could contribute significantly to the soundscapes if these insects are present in large numbers. Amphibians such as frogs and toads rely primarily on vocalizations to attract mates Gerhardt In the northern temperate regions of eastern North America, spring peepers Pseudacris crucifer are common singers at night in wetlands and ponds.

Calls are intense during the breeding seasons, which extend from late winter February to early spring May in the northern United States and from late fall October to early spring March in more southern locations. Frequencies of frog and toad choruses range from 2 to 5 kHz. Almost all birds use sound to attract mates, defend territories, sound alarms, and communicate other types of information. Many of the passerines are especially known for producing elaborate songs Kroodsma Most songs and calls produced by birds occur in the 2 to 6 kHz range.

The acoustic frequency of a bird's song relates to its body size large-bodied birds produce sounds as low as 1 kHz and habitat type and structure; for example, some tropical birds use protracted pure tones in environments with persistent geophonic sounds of wind and rain, and some vocalizations reach frequencies in the 10 to 12 kHz range Kerry Rabenold, Department of Biological Sciences, Purdue University, West Lafayette, Indiana, personal communication, 5 October A variety of terrestrial mammals also produce sounds McComb and Reby Groups that are frequent contributors of sound produced in landscapes include primates e.

The second, communication calls, are more readily audible to humans and are used to identify individuals. Recently, considerable evidence has emerged showing that anthrophony can influence animal communication in a variety of ways. For example, American robins Turdus migratorius shift the timing of their singing in urban environments to the night Fuller et al.

In song sparrows Melospiza melodia , the lowest-frequency notes were higher in environments with high ambient noise Wood and Yezerinac Brumm found that free-ranging nightingales Luscinia megarhynchos in noisier environments sing more loudly than those in quieter environments, and Slabbekoorn and Peet determined that the great tit Parus major sings at higher pitches in urban noise conditions. Rhythms of nature.

The sounds of nature contain numerous rhythms or cycles. Many recognized temporal cycles of communication occur in terrestrial animals, the most well studied being those of birds, amphibians, and insects.

Dawn chorus in birds is thought to occur when individuals, arriving back to their territory, use songs to advertise their presence Staicer et al. This circadian pattern of singing in birds, the timing of which is largely affected by weather and climatic conditions, strongly correlates with sunrise and sunset and becomes more pronounced with the onset of breeding and migration.

We believe that we are now well poised to place soundscape ecology into a more research and application focus. Research is needed in several new areas, organized around the following main themes: measurement and quantification, spatial-temporal dynamics, environmental covariates, human impacts on soundscapes, soundscape impacts on humans, and soundscape impacts on wildlife. Theme 1: Improve the measurement and quantification of sounds. Acoustic sensors are needed that can automate the recording of sounds, that are inexpensive, and that can be placed in large networks in hostile environments.

Research is required that can automatically differentiate all sounds emanating from landscapes. For example, researchers need tools that can classify biological, geophysical, and anthropogenic sources of sounds. Scientists also need a better understanding of how these sources of sounds differ in their composition.

How do anthrophonic sounds differ in composition acoustic frequency, time interval from biophonic sounds? Is the presence of certain kinds of sounds indicative of a healthy or deteriorating landscape?

In situ measurements of biodiversity need to be compared with soundscape measures to determine how well vocal organisms provide a proxy for biodiversity in general. Research in this area can also advance our ability to use soundscape measures for natural resource management and biological conservation. Theme 2: Improve our understanding of spatial-temporal dynamics across different scales. Research is needed on how soundscapes vary with landscape patterns and processes figure 1 , arrows 1 and 2.

How do soundscapes differ with land-use patterns? Comparisons of soundscape dynamics should be made of various natural ecosystems around the world but also across areas that differ in the amount of human disturbance within an ecosystem. Vertebrate species richness has been shown to vary with vegetation structure canopy height, density. Is soundscape diversity greatest where vegetation structure is most complex? More research is needed that attempts to characterize the different types of the temporal patterns of soundscapes.

How do soundscapes vary over different time frames seconds, minutes, hours, diurnally, annually figure 1 , arrows 4 and 5 in different landscapes? How are the dawn and dusk choruses affected by human activities? Theme 3: Improve our understanding of how important environmental covariates impact sound. Biophonic and geophonic sounds very likely vary according to many environmental factors, such as weather, plant phenology, and elevation. Specific research is needed on how soundscapes vary by temperature air, soil, and water , solar radiation, lunar radiation, relative humidity, heating degree days, and moisture budgets figure 1 , arrow 4.

Knowledge of these covariates will be necessary as researchers attempt to understand how human activity impacts natural soundscape dynamics.

Studies on how geophonic sounds of wind, running water, and rain affect biophonic patterns will help us to understand the plasticity of biological communication as it relates to human-generated sounds.

Theme 4: Assess the impact of soundscapes on wildlife. There is a need for more research on how certain soundscape qualities e. Research is required on the ways anthrophony affects wildlife behavior, such as breeding, predator-prey relationships, and physiology. As soundscape patterns such as signal composition, sound diversity, and temporal cycles change, what are the impacts to species' life-history patterns?

Theme 5: Assess the impacts of humans on soundscapes. Humans create many objects that produce sounds figure 1 , arrow 5. How do engines, road noises, bells, sirens, and other machines affect soundscape composition? As new technologies emerge, how do these affect the soundscape? What policies are needed to protect soundscapes in various settings such as national parks or our cities and neighborhoods? How can land-use planners and policymakers determine future soundscapes?

Theme 6: Assess soundscape impacts on humans. Humans are surrounded by sounds that emanate from the environment and these sensory connections to nature are from the soundscape figure 1 , arrow 7.

Research is needed on how natural sounds influence the development of individuals' sense of place, place attachment, and connection to nature.

More specifically, how do human demographic variables such as culture, place of residence, or age affect the strength of human values associated with soundscapes? What factors affect human in tolerance of soundscape changes, especially where those changes increase noise? We present four case studies that illustrate various aspects of soundscape ecology. These studies also exemplify the kinds of research that can be conducted across the six research themes posed above.

The first case study, which is not a separate study in itself as are the three others, represents selected recordings from the massive Krause year-old soundscape archive.

Krause, a musician and recording engineer, has recorded natural sounds for use in the entertainment industry. A third study, conducted in Sequoia National Park in the United States, attempts to determine whether organisms are partitioning their sounds and the extent to which geophonic sounds, such as rivers and wind, interfere with animal communication.

The final study, conducted in montane forests in Tuscany, Italy, centers on mapping dynamic soundscapes. Krause ambient sounds soundscape archive.

We use several field recordings that are part of the massive Krause soundscape archive to illustrate how sounds reflect certain characteristics of landscapes and the organisms that live within them. A 1-minutesecond recording of a tropical forest in Madagascar in sound file 6 represents an excellent example of the ANH, exemplifying that sounds produced by animals are separated in space, time, and frequency.

Here, dozens of birds vocalize with little frequency or temporal overlap. One bird probably a sickle-billed vanga, Falculea palliata produces four rapid calls followed by a brief pause at 1 kHz, much below the frequency of other bird vocalizations.

This recording most likely represents some of the greatest acoustic niche separation in the world. The nighttime recording of organisms producing sounds in a bai in the Central African Republic sound file 7 illustrates how unique landscapes can create unique soundscapes. Here, the normal synchronous production of nighttime sounds by insects and frogs is interwoven with the loud trumpeting, bellowing, and grunting of forest elephants Loxodonta cyclotis.

A bai is a special landscape where forest elephants go areas have been cleared by elephants because of the high salt content of the mud surrounding ponds created by groundwater upwelling; thus, landscape structure and the specific animals occupying these areas can create a unique soundscape. A recording sound file 8 of the dawn chorus in Zimbabwe illustrates not only the complexity of sounds produced in the morning but also animals' use of special landforms to propagate calls.

The first minute contains a typical chorusing of about 30 different species of birds see supplementary online materials at www. At into this recording, however, baboons Papio cynocephalus begin to bark. The landform is thus exploited by these animals to propagate their voices.

Many animals, such as African lions Panthera leo , forest and plains elephants, and hyenas, choose the time and place to make their voices echo.

Wiens and Milne , among others, have emphasized the need to understand landscapes from the perspective of the size of an organism; they found that from a beetle's point of view, the very fine structure of a landscape influences movement patterns. Additionally, many insects produce sounds that aid in breeding or communication that may not be audible to humans or to other organisms in the landscape.

Do you describe the homes, shops, and businesses? Do you describe the people? Maybe you describe the landscape. All of these natural and human-made things help to define your sense of place, or what makes a certain place have its own distinctive character. When people describe places, sound is often forgotten. But sound is often a major part of what makes a place special—what gives it a "sense of place. What is it? Why does it make you think of your home?

Explore how sounds define a sense of place. Think about another place you are familiar with, such as a grocery store, a bus stop, or a neighborhood park.

What are some of the distinctive sounds in those places? Would the grocery store sound like a grocery store without the sound of shopping carts clanging together in the cart corral and the beep of the checkout counters? Would a bus stop sound like a bus stop without the sound of the engine mixing with the whoosh of the doors opening?

Would the park sound like a park without the sound of children playing? Listen to the sounds around you. Close your eyes and listen to the sounds that are surrounding you right now. They might be natural or made by humans. You might hear the hum of your computer, birds outside your window, or your family members laughing. All of these sounds build a soundscape. Think about how a landscape is made up of all of the different landforms, trees, houses, yards, and roads. A soundscape is made up of all of the different sounds that help to create a sense of place in your home.

Walk around your home or apartment for a few minutes. This could be the soundscape of a nineteenth century household, even a specific nineteenth century household. In an environmental context, the soundscape helps us understand the acoustic ecology of a place.

A forest filled with many types of birdsong and other animal activity would indicate a healthy, diverse, and resilient ecosystem. Conversely, an ecosystem dominated by a single sound source, such as the buzz of the cicada, illustrates a potential lack of diversity and resilience. The more resilient an environment is, the greater its ability to weather a significant disturbance without irreparable harm and change. Also important are the ways in which sounds interact with each other.

Competing noise arising from human activity forces organisms to alter their behavior to adapt to new frequencies, like traffic. Human communities are no different. The distinction between sonic facets of communities is increasingly difficult to discern at the surface level. Much like a cicada call, the blare of Western pop music in restaurants and taxi cabs dominates soundscapes across the globe.

Acres of Brazilian rainforest have given way to cattle ranches and pastureland, bringing with them completely new soundscapes and soundmarks. However, even among this change, it is important to remember that underneath the seemingly homogenous surface, rich cultural wells still exist in the form of grassroots music, storytelling, and industry. All these require is a little amplification to be heard. The human experience is highly sonic.

Because one of the core properties of sound is its ephemerality—it does not endure long past its production, and even a recording is but a subjective representation of reality—it is easy to forget, even though it is one of our primary senses.

Print Share: Facebook Twitter Email. What you will need: A "blind-friendly" stereo recorder. Olympus sells a wide variety of recorders, many of which have spoken menus and accessible buttons. Related Blog Posts.