It sounds like the noise is not coming in from a specific location. However, you may want to do a little investigation and see if there are any "point sources" of noise. HVAC vents come to mind. In the house I grew up in you could clearly hear people in other rooms of the house through the vents that connected the rooms. Just a thought. My only other suggestion is to use the squishy foam earplugs contractors use. I've used them to sleep while camping etc. they aren't too uncomfortable.