page_title: Soundscape ecology
section_title: Description
hierarchical_section_title: Soundscape ecology / Description
context_page_description: Soundscape ecology is the study of the acoustic relationships between living organisms, human and other, and their environment, whether the organisms are marine or terrestrial. First appearing in the Handbook for Acoustic Ecology edited by Barry Truax, in 1978, the term has occasionally been used, sometimes interchangeably, with the term acoustic ecology. Soundscape ecologists also study the relationships between the three basic sources of sound that comprise the soundscape: those generated by organisms are referred to as the biophony; those from non-biological natural categories are classified as the geophony, and those produced by humans, the anthropophony.
  Increasingly, soundscapes are dominated by a sub-set of anthropophony, or technophony, the overwhelming presence of electro-mechanical noise. This sub-class of noise pollution or disturbance may produce a negative effect on a wide range of organisms. Variations in soundscapes as a result of natural phenomena and human endeavor may have wide-ranging ecological effects as many organisms have evolved to respond to acoustic cues that emanate primarily from undisturbed habitats.
context_section_description: Soundscape ecology serves as a lens into other fields including medicine, music, dance, philosophy, environmental studies, etc. (the soundscape). The soundscape of a given region can be viewed as the sum of three separate sound sources:
  Geophony is non-biological in nature, consisting of the effect of wind in trees or grasses, water flowing in a stream, waves at an ocean or lake shoreline, and movement of the earth.
  Biophony is a term introduced by soundscape ecologist, Bernie Krause, who in 1998, first began to express the soundscape in terms of its acoustic sources. The biophony refers to the collective acoustic signatures generated by all sound-producing organisms in a given habitat at a given moment. It includes vocalizations that are used for conspecific communication in some cases.
  Anthropophony is another term introduced by Krause along with colleague, Stuart Gage. It represents human generated sound from either humans, themselves, or the electro-mechanical technologies they employ. Anthropophony is divided into two sub-categories. Controlled sound, such as music, language, and theatre, and chaotic or incoherent sound sometimes referred to as noise.
  Various combinations of these acoustic expressions across space and time generate unique soundscapes.
  Soundscape ecologists seek to investigate the structure of soundscapes, explain how they are generated, and study how organisms interrelate acoustically. A number of hypotheses have been proposed to explain the structure of soundscapes, particularly elements of biophony. For instance, an ecological theory known as the acoustic adaptation hypothesis predicts that acoustic signals of animals are altered in different physical environments in order to maximize their propagation through the habitat. In addition, acoustic signals from organisms may be under selective pressure to minimize their frequency (pitch) overlap with other auditory features of the environment. This acoustic niche hypothesis  is analogous to the classical ecological concept of niche partitioning. It suggests that acoustic signals in the environment should display frequency partitioning as a result of selection acting to maximize the effectiveness of intraspecific communication for different species. Observations of frequency differentiation among insects, birds, and anurans support the acoustic niche hypothesis. Organisms may also partition their vocalization frequencies to avoid overlap with pervasive geophonic sounds. For example, territorial communication in some frog species takes place partially in the high frequency ultrasonic spectrum. This communication method represents an evolutionary adaptation to the frogs' riparian habitat where running water produces constant low frequency sound. Invasive species that introduce new sounds into soundscapes can disrupt acoustic niche partitioning in native communities, a process known as biophonic invasion. Although adaptation to acoustic niches may explain the frequency structure of soundscapes, spatial variation in sound is likely to be generated by environmental gradients in altitude, latitude, or habitat disturbance. These gradients may alter the relative contributions of biophony, geophony, and anthrophony to the soundscape. For example, when compared with unaltered habitats, regions with high levels of urban land-use are likely to have increased levels of anthrophony and decreased physical and organismal sound sources. Soundscapes typically exhibit temporal patterns, with daily and seasonal cycles being particularly prominent. These patterns are often generated by the communities of organisms that contribute to biophony. For example, birds chorus heavily at dawn and dusk while anurans call primarily at night; the timing of these vocalization events may have evolved to minimize temporal overlap with other elements of the soundscape.
caption: Sounds produced by physical features of the environment such as running water contribute to natural soundscapes
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