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Bioacoustics is historically adiscipline that essentially focuses on individual behaviour in relation to population and species evolutionary levels butr arely in connection with higher levels of ecological complexity likec ommunity,landscape or ecosystem. However, some recent bioacoustic researches have operated ac hange of scale by developing acoustic indices which aim is to characterize animal acoustic communities and soundscapes. We here reviewt hese indices for the first time. The indices can be divided into twoc lasses: the α or within-group indices and the β or between-group indices. Up to 21 α acoustic indices were proposed in less than six years. These indices estimate the amplitude, evenness, richness, heterogeneity of an acoustic community or soundscape. Seven β diversity indices were suggested to compare amplitude envelopes or,more often, frequencyspectral profiles. Both α and β indices reported congruent and expected results buttheymay still suffer some bias due, for instance, to anthropic background noise or variations in the distances between vocalising animals and the sensors. Research is still needed to improve the reliability of these newmathematical tools for biodiversity assessment and monitoring. We recommend the contemporary use of some of these indices to obtain complementary information. Eventually,weforesee that this newfield of research which tries to build bridges between animal behaviour and ecology should meet an important success in the next years for the assessment and monitoring of marine, freshwater and terrestrial biodiversity from individual-based leveltolandscape dimension.

The sounds produced by animals have been a topic of research into animal behaviour for a very long time. If acoustic signals are undoubtedly a vehicle for exchanging information between individuals, environmental sounds embed as well a significant level of data related to the ecology of populations, communities and landscapes. The consideration of environmental sounds for ecological investigations opens up a field of research that we define with the term ecoacoustics. In this paper, we draw the contours of ecoacoustics by detailing: the main theories, concepts and methods used in ecoacoustic research, and the numerous outcomes that can be expected from the ecological approach to sound. Ecoacoustics has several theoretical and practical challenges, but we firmly believe that this new approach to investigating ecological processes will generate abundant and exciting research program