I have lived in this house for more than 20 years. It has never had a gurgling noise like this. There are only two things that have occurred that I think might influence the gurgling. In january, I had the waste line cleaned out since we live in a rural area and have a leach field. It did not appear to do this after the line was snaked out by the plumber. He said some roots were clogging the line into the 1000 gal septic tank but wasn't really serious. The other thing is that I increased the well pump shutoff and on cycles to keep at least 60 psi high level and kick on rate of 45 psi. This only happens when the toilet is flushed.