Not even SEEING. Just HEARING it.
http://www.greater-yellowstone.com/animals/beavers.html
"A beaver’s desire to build a dam is very instinctive; they seem to not be able to tolerate moving water, as it must be stopped. Beavers in captivity will build useless dams just so they can build. In the wild, scientists have observed beavers making repairs and additions to human-made dams. Beavers hate the sound of running water. It makes them think there could be a leak in their dam. If they hear running water, they will often work day and night to find the leak and repair it. A Jackson Hole rancher, Chancy Wheeldon, one day built a pond all, but the spillway, which he would complete the following day. The following day he awoke to find beavers had finished his dam that leaked the perfect amount to regulate stream flow."
Another good one:
https://auduboncnc.org/beavers-and-beaver-deceivers-by-jeff-tome/
"They seem to be motivated by the sound of running water and dam up areas to stop that sound.
Researchers, both in zoos and in the wild, have played the sound of running water for the beavers. It only takes a night for the speakers to be covered with mud and sticks until the sound could not be heard."