Ced
because they are scared . And they have very good hearing and if you heard a load noise would you panic?! i think you would lol
First are there floor drains in basement? Could have blockage and force through floor drains. Plus there could be a parcel blockage in pipe and wax seal in toilet is shot. So when pipe fills it leaks at wax seal. Could be broken pipe that is existing some where in system. If unfimilar with plumbing, call a plumber. In some cases this will let you put your energy in other places. As far as the mold, get a dehumidifier. Sized right for the application. Hope this helps.