Noise Becomes Stronger
At first, they would hear the noise every now and then. It wasn’t very loud and even if one person would hear it, another one would not. It simply wasn’t a big deal and they got used to it. Add the fact that the noise would manifest itself rarely and you can see why these people weren’t worried about the noise and the house.
But they started noticing that the noise would become stronger and it would manifest more frequently. More people would notice that noise. This is the time when they started to be suspicious and they were worried about the home. The problem looks like it will become worse and worse as time passes by.