This sound is tinnitus. It cannot be heard externally by anyone else as it is the mind's perception of sound. I have had it in both ears for decades. You can't get rid of it, unfortunately as there's no cure. My way of dealing with it is to keep busy. Others listen to music, white noise, radio in background etc. Some do therapy. For me it's annoying, not life ruining, so I just cope. Your wife might want to look up sites specific to tinnitus.