An Introduction to Ecoacoustics

Abstract

Ecoacoustics is a new discipline that aims to investigate the ecological role of sounds of geological, biophonic, and anthropogenic origin. Its development has been favored by new robust theoretical principles associated to efficient metrics for data processing and by the availability of autonomous acoustic recorders to collect a great number of acoustic files at different temporal and geographical scale.The double role of sound as a semiotic tool to communicate and as ecological proxy of environmental conditions to select habitats and to navigate represents the ideal condition for a rapid development of this discipline. The transformation of latent vibrations as generators of any typology of sound, a clear semiosis that recognizes a sonoscape as the component of the original vibroscape sensed by organisms, and a soundscape as the portion of sonoscape interpreted by individual species are three components of the sonic domain. Sonotope and soundtope, respectively, are sensed and interpreted patches with which soniferous species and acoustic communities interact in a spatial sonic mosaic.The Morphological Adaptation Hypothesis, the Acoustic Adaptation Hypothesis, the Acoustic Niche Hypothesis, the Acoustic Community Hypothesis, and the Acoustic Habitat Hypothesis represent the theoretical fundaments of ecoacoustics.An acoustic community is defined as the collection of soniferous species acoustically active in space and time. Such aggregation of soniferous species determines a sonic environment variable in space and time and represented by sonic matrices (on which to apply ecoacoustics metrics) after a process of migration from a temporal domain to a frequential domain via a Fourier Transform. A large portion of ecoacoustic investigations focuses on the role of noise (especially of anthropogenic origin) on behavioral and ecological processes in terrestrial and in aquatic ecosystems.To describe the complex sonic domain where an originator vibroscape evolves into several distinct objects obtained after a latent, sensed, and interpreted semiosis requires the development of a dedicated narrative. Sonoscape is the result of a sensed vibroscape, and a soundscape is obtained from an interpreted sonoscape. Sonotopes represent the “geographical” elements composing a sonoscape, and their detection is obtained by the deployment of sound recorders according to a configuration that enhances the spatial heterogeneity. Sonotopes are the spatial unit of a sonic information system and represent the link with the geographical character of a landscape. Every sonotope is characterized by species-specific sonic and acoustic signatures. The former (species-specific sonic signature) is the result of a sensed vibroscape and the latter (species-specific acoustic signature) of the interpretation of sonic signals.Ecoacoustic events obtained by coding three metrics (ACIft, ACIft evenness, and ACItf evenness) are an attempt to discretize acoustic signals into functional or statistical distinct units.