Hi Daisy,
I think it is MS related, a lesion in that area of the brain. Many MS sites says that.

I get that quick loss of hearing for a few minutes and hate it. Then mine goes back to just the ringing or hissing sound. That still is not normal.

I was checked by a ENT doctor and he said my hearing was normal. Duh! I hear distant sounds before voices. So I ask people to repeat themselves. That doctor said no hearing device will help.

That doesn't seem normal. But if you put their headset on, and get tested, you may appear to be normal. That is what happened to me. The guy was talking right into my head.

I have had it 24/7 since 1995. I just ignore it. It it can't be fixed or treated than I ignore it.

Then many normal people have this too. Maybe theirs is treatable. Mine isn't. My Neuro back then confirmed that.

So MS related or not, get a hearing test to be sure.