Low Frequency Noise inside my house
Many lift stations now use what are called "VFDs" (Variable Frequency Drives) to control the speed of the pumps. So instead of allowing the tank to fill up to trigger a pump to run full speed until it pumps down again, they use a continuous level monitor system and change the pump speed to adjust for variations in flow and the pumps never (or rarely) completely stop. 

VFDs can cause electrical distribution transformers to make noise (due to what are called "harmonics"). If you are hearing this as an audible hum, it may be something they can fix, but they won't do it unless you complain.

The other possibility is that this is a mechanical issue with the pumps causing actual mechanical vibrations (seismic) getting to your house under certain circumstances that are conducive to that transmittal, i.e. ground moisture conditions are just right. In that case they SHOULD fix it, because it is an impending equipment failure. They may not know, so either way you should tell them.