White's Tree frogs are known to croak when there is a change in the atmospheric pressure, in other words when there is a storm in the forecast. Nearly every time before it rained or during a storm, my White's tree frog would croak. However, sometimes my frog does croak to the sound of the vacuum or to heavy static on the radio. There could be a certain frequencies in those certain noises that we humans are not sensitive to, that white's are able to detect. Those frequencies could be the same frequencies that are found in a White's call. For a project on frog vocalizations, I have played back calls that I recorded of my White's; every time he responds back to his own calls. It's pretty interesting to watch.