Under florida are numerous caverns. As the new madrid fault gets ready to blow, air and water is pushed up thru the caverns, making weird rumbling sounds.

Another major problem is you sit on a huge methane glacier that bp drilled into. When the oil came out, seawater rushed in at some other places. And that is dissolving the surrounding minerals from the earth that kept the glacier safe.
Now it is reacting chemically, and probably breaking apart. That can also cause the noises you heard. Because some of it will come to the surface thru the caverns.