@lineage
Hello,
I am not sure if I am steering you in the right direction but your post reminds me of a condition called Pulsatile Tinnitus where you can hear your heartbeat or pulse in your ears. I understand a lot of people hear this sound when resting or lying down. The ear is very sensitive to blood flow and has a relationship to the heart. May I suggest you have a thorough medical check up which includes an EKG. Any type of Tinnitus can be constant or intermittent and a lot of people don’t notice it during the day when they are absorbed in the daily routines of life.
Don’t let your primary doctor blow this off . It is a concern to you so it is important even if it turns out to be minor. By the way I have “ordinary” tinnitus in one ear.

Regards from a Florida Mary