Well it could be that you indeed do have a Eustacian Tube issue.

Since you hear it,  I think it is indeed in that area.   I don't think a sinus
connection is likely, although you could have an infection from one migrating
to the other.

I would be careful about trying to do anything radical about it such as
surgery.  The "cure might be worse than the disease."    It may go away in
time.

I have had it too.

The opening of the Eustacian tube is probably inflamed or infected or ....

I had a mild  hearing loss for literally years in one ear, including
hyperacusis etc.  
A number of  "ENT's" told me there was nothing abnormal.
I had ETD diagnosed by one "ENT"  using sophisticated instrumentation.
"Abnormally patent" I think he said.

Then it went away.  I do not think this area is completely understood.  

You woudl have to get more second opinions if you really wanted to pursue it.

(I put "ENT" in quotes because I cannot stand that abbreviation because it is
technically incorrect diction to call  a doctor by a  list of body parts)