Soft static or faint blowing noise of the running refrigerator
Inconsistent ringing or ghostly howling of the bathroom’s toilet that goes off every now and then
Rumbling, small squeaks and creaks, and high-pitched voices from the movement and activity of the neighbor living upstairs
The heater has a small popping noise that sometimes turns into a knocking noise. When I was younger, I imagined the sound as that of medieval knights jousting for some reason
A short yet fast ringing that plays quietly in the background in an empty room, exemplified and turning into loud muffles when I yawn