Hearing things that aren't there (maybe stress related)?

Over the past 6-7 months I've been dealing with a lot crap around the house and more stress than I've ever dealt with before. One of the things that would happen often and something bad would follow would be a loud crash/bang noise. Now I hear that noise randomly even though nothing's fallen or caused it. But I keep hearing it. It sounds exactly like the sound from early this year. The only explanation I can count as a possibility is PTSD but the closest symptom that has to what I'm experiencing is the flashback triggers. Like a sound bringing you back to the stress. But the sound is there all on its own. Nothing triggered it. What could it be?