Here are some USGS Web pages with more information on vocalization methods and Anywhere:
North American Amphibian Monitoring Program (NAAMP)
The North American Amphibian Monitoring Program (NAAMP) is a long-term monitoring program designed to track the status and trends of frog and toad populations with links to data access, protocol, and how to volunteer as an observer.
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Definition:
Series of methods used to (a) record sonograms (sound spectrogram) of animal sounds which are analyzed to identify the presence of species in an area and to determine distinct sound patterns within a species, e.g., mating calls, danger alerts; (b) attract species to an area for inventory or monitoring by playing recorded animal sounds or mimicking them.