The Soundscape A Peculiar Landscape

The term soundscape has been used by Ray Murray Schafer (1977) to indicate the spatial and temporal distribution of sound in natural and human-modified ecosystems.

The soundscape is a highly dynamic field of energy and information that has a quite low persistence in time and space. Every acoustic activity from natural processes like a thunderstorm, a water fall, a marine wave or wind and from organisms

(bird song, mammal vocalizations) create a spatial acoustic map that can be used by organisms to explore the surroundings.

A huge amount of literature on song, alarm and vocal communication describes functions and patterns of this universal semiotic mechanism (Hopp et al. 1998). But the soundscape can also be considered a peculiar "scape," an organized energetic and informative field used by organisms to increase the semethic connection and to expand the semiotic niche (sensu Hoffmeyer 2008), and to partition communication space between competitive species (Luther 2008).

Hoffmeyer recently wrote: "The idea behind the concept of the semiotic niche was to construct a term that would embrace the totality of signs or cues in the surroundings of an organism - signs that it must be able to meaningfully interpret to ensure its survival and welfare." The semiotic niche includes all the components of the ecological niche but in addition allows organisms to distinguish relevant from irrelevant items and threats and represents the "externalistic counterpart" to the Umwelt concept (Hoffmeyer 2008).

Sounds are the result of a huge energy investment as demonstrated by empirical and experimental evidences (Truax 2001). Communication is seen as the main reason for acoustic cues. But recently we have posed further questions on this subject. Despite a great amount of literature on this subject, especially for birds, marine mammals, bats, and insects (Hopp et al. 1998) largely unknown remain the use of sounds for other purposes. The interesting hypothesis that sounds are used not only to communicate but also as indicators of resources or to locate possible competitors and predators seems confirmed by our recent unpublished results. Using a matrix of sound recorders it has been possible to collect information about intensity and frequency of bird acoustic activity and by a complex elaboration to extract the distribution of sounds across a spatial and temporal surface. We call such a surface a soundscape in which it is possible to observe the tridimensional shape of selected frequencies. With this methodology it is possible to investigate the distribution in space and time of sounds and to interpret the complex patterns created by interspecific interactions. The use by an individual of the spatial distribution of sound perceived around that individual could represent an acoustic eco-field when we assume that some resources can be localized using such a strategy. For instance, the alarm call of a tit, informs other individuals or other species about the presence of a potential risk (man or predator). At the same time, the call of a chaffinch could be used by another chaffinch to find a foraging place. Bird song is used to delimit a breeding territory but also to attract females and chase intruders.

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