A ways back I had tin can sound and when I spoke it was like I had speaker in my head. At the time, I was on prednisone and had PMR and had lost lots of weight. I researched and found that sudden weight loss can result in Autophony which is classic, hallmark symptom of a patulous eustachian tube. It is a condition in which you hear unusually loud feedback of your own voice, breathing, and heartbeats. ENT wanted to put in tubes but I just gave it time and eventually it fixed itself.