Acoustic conditions affecting sound communication in air and underwater

Biodiversity across the animal kingdom is reflected in acoustic diversity,
and the evolution of these signals is driven by the ability to produce and hear sounds within the complex nature of soundscapes. Signals from the sender are attenuated and their structure is changed during propagation to receivers, and other sounds contributing to the soundscape can interfere with signals intended for the receiver. Therefore, the message encoded in the sender’s signal may be difficult or impossible for the potential receiver to decode unless the receiver adapts behaviorally. This chapter discusses the potential effects of sound propagation and environmental sound on communication both in air and underwater. First, the wave equation is defined; second, attenuation, absorption and scattering principles are discussed in relation to physical sound propagation effects on the sender’s signal; and third, abiotic, biotic, and anthropogenic sources of environmental noise are introduced and discussed. Environmental noise is present in all habitats, and soundscapes are getting louder, in part mostly due to increased anthropogenic noise inputs. Therefore, animals that rely on sound to communicate have to adapt and evolve to their local
soundscape to get their message across.