Hi Carrigon and all. I have had this problem since my cfs and pots got very bad 9 years ago. It goes through phases of being very bad, so loud that I can't hear small sounds around me eg foot steps approaching.When it's less bad it sounds like an incessant whooshing which is annoying but not as bad as the hard beating. I find it gets worse when my general cfs and pots are worst.
I haven't found anything that helps except placing my hand up along the side of my neck and pressing lightly. That seems to stop it but only while I'm holding it.I need to do this if I want to hear small sounds around the house or wind outside. Sticking one ear plug into my right ear,which is usually worse than the left, also helps give some relief too. It kindda depends on the angle you place it at to help though. It's trial and error.
I wish I had a more hopeful story of it going away altogether but I can say you do get used to it and it gets less annoying and eases as you feel better.I've been severely affected for a long time now but the last time I felt a bit better it eased quite a lot. Hope it help to feel you aren't alone with it. I find it comforting to think I'm not.
If anyone has any tips for managing it or improving it I'd love to hear them.