You don’t mention it in your profile, but Mom has dementia? Unfortunately, this disease causes hallucinations, delusions and paranoia. My mom had all three. The facility she was in dealt with it the best they could, but many times I’d hear that she was up all night walking the halls or yelling that someone was in her room. The staff told me they didn’t try to convince her that no one was there, because in her mind, someone was. These people worked the night shift so they could go home and rest during the day, but since you live with your mom, you cannot do that. When my mom’s delusions got so bad that she was up night after night after night, they called in the house doctor and he prescribed a low dose of a sleep aid. It did seem to help her.
Bonella, one suggestion is to have Mom tested for an Urinary Tract Infection as such an infection can cause elders to believe there are things that don't exist, plus a lot of other different symptoms.
When my Dad had a UTI, he was seeing ants on the wall and in his food. Once the antibiotics kicked in, the "ants" started to go away.
Sometimes there's a reason why they think they are hearing something... sometimes they are. My mother was hearing someone talking outside the house, which I thought was not happening. Then one night I got up to refill my water glass and heard voices as I stood in the kitchen. I looked out a window and saw my neighbors out on their front porch with their dogs at 2:30a and I could hear their voices. I went back to my mother's room and although Mom was sound asleep, I could hear the neighbor's voices. I could not hear them from my bedroom or the living room on the other side of the house.
If this is dementia and there is truly no noise you will need to accept that for her there IS noise, and you can make up a reason if you like, that you have some loose siding and it sounds just exactly like what she thinks she is hearing. Just don't try to convince her she is NOT hearing it, because the terror of thinking you are out of control will cause more anxiety and more hallucinations. My brother has the beginnings of what they believe is a Lewy's Bodies Dementia. Any anxiety makes him see things more. He is aware this is happening to him and will discuss in great details the things he sees. But when he hears things he has more difficulty believing it is not true. The phone is a problem for him, he will hear things on the line of he will not hear me speaking and begin to say "hello! Hello!!!!". As we don't live in the city it makes it difficult and in the beginning of it he would call the phone company--poor guys would check and it was fine. He has a hard time accepting it is "him", whereas visual hallucinations are easy for him to decide are not true, though very realistic. As I said, anxiety makes his much worse, and since he has entered assisted living and made me trustee of his trust so financial stuff is taken care of there has been so much less anxiety and so many fewer hallucinations visual or auditory, and this is why I suggest no arguing and keep calm as able. Perhaps a soft radio or tape with rain falling or something like that may help, but could make it worse as well. Just feel your way through the best you can.
When my Dad had a UTI, he was seeing ants on the wall and in his food. Once the antibiotics kicked in, the "ants" started to go away.