The niche hypothesis, also known as the acoustic niche hypothesis (ANH), is an early version of the term biophony. The term describes the acoustic bandwidth partitioning process that occurs in still-wild biomes by which non-human organisms adjust their vocalizations by frequency and time-shifting to compensate for vocal territory occupied by other vocal creatures. Thus, each species evolves to establish and maintain its own acoustic bandwidth so that its voice is not masked. For instance, notable examples of clear partitioning and species discrimination can be found in the spectrograms derived from the biophonic recordings made in most uncompromised tropical and subtropical rain forests. Additional studies with certain insects and amphibians tend to confirm the hypothesis.
The term was first coined by soundscape ecology early practitioner, Bernie Krause.