I have the same issue its as if there is a ultra sound heart beat in my ear. It comes and goes as it pleases as well. I got it around a month ago and i thought it would go away but it only seems to be getting worse. I have heard that it might be sinuses or something worse. But i did see a family doctor and he looked in my ear and saw no infection and than so he sent me to get a head scan! i find out what my results are tomorrow and would be glad to let you know what my results were so you might have an idea of how serious this might or might not be. But i have notice that if i turn to the left ( also the ear in which is having the heart beat sounds) it goes away.

I had the same problem.
During 6 seconds i could measure my heartbeat in my ear (sitting in a train)
The reason was that my bloodpressure was too high.
Cardiologist gave me Ramipril and it was gone.