I captured this soundscape during the green frog breeding season in Litchfield, CT. Setting up my equipment near a pond where they had congregated to compete for call time and recognition, I was able to listen to and record some very vigorous calls. Males song an accented 'twang' sound, similar to the banjo, or in my opinion, more akin to the sanxian, which is a Chinese three-stringed fretless lute which is plucked.
Acoustic communication is essential for the frog's survival in both territorial defense and in localization and attraction of mates. Sounds from frogs travel through the air, through water, and through the substrate (the surface where a plant or animal grows on).
Unfortunately, for female frogs, increasing noise from nearby traffic, airplanes, construction and other human ambient noises have been shown to slow their abilities to listen for and locate male frogs that are calling for their services during the mating season. Unfortunately, many species of frogs have struggled to adapt their calls to the growing demands of increased environmental noise, which environmentalists say could lead to less reproduction and declining populations of these frogs.
Frogs produce a rich variety of sounds, calls, and songs during their courtship and mating rituals. The callers, usually males, make stereotyped sounds in order to advertise their location, their mating readiness and their willingness to defend their territory; listeners respond to the calls by return calling, by approach, and by going silent. These responses have been shown to be important for species recognition, mate assessment, and localization.
Females must recognize the male they choose by his call. By localizing where his call is coming from she can find him. An additional challenge is that she is localizing his call while listening to the many other frogs in the chorus, and to the noise of the stream and insects. The breeding pond is a very noisy place, and females must distinguish a male's calls from the other noise. How they recognize the sound pattern of the male they are pursuing from the surrounding noise is similar to how intelligent hearing aids help people hear certain sounds and cancel out others.