Dad with mixed dementia keeps hearing noises.

My dad has Mixed dementia and on occasion is unable to relax and sleep because he keeps hearing noises not there. Anyone have suggestions on how to help him or any tricks that help quiet the noises? My mom says it’s everything from clock ticking, tractors, cars, buzzing alarms and gas leaking to name a few. Today seemed to be worse so he’s been unable to relax or nap today. At this point he’s still up later than usual forhim if he hasn’t napped.