Strange low drowning sound

I have been noticing a strange drowning sound almost like a train starting up or an old car thats driving too fast.

I can only hear this low rumbling drowning sound when indoors
its as if the house is resonating but if I step outside the sound vanishes.

I live 10 km from the highway and live in a small town though we do have trains pass threw our town there only 1 or 2 a day and this sound seems to happen all the time but not constant it fades away and picks up.

I have been noticing this strange sound for about a month now and have lived in this house for about 15 years. I have also seen other people posting about hearing a strange low drowning rumbling sound coming from no where I just cant explain whats causing it.

Central Alberta