I do hear my heartbeat from my left ear. The ear doctor said that the ear can be sensitive to the blood flowing from nearby arteries, and that there's nothing to do. Stress affects the heartbeat volume. I just got used to it, but it can be annoying sometimes, especially when you're trying to enjoy the silence.

The doctor also told me that it's not an ear problem, but rather a brain problem. The brain is supposed to filter out this noise, in the same sense that it filters out the sounds from a (normal) digestion, our breathing, etc. I do have some (undiagnosed) hypersensitivity, so that sounds consistent to me.

nozzlegear: it gets better with time, the less you think about it. I know it's not a great consolation, but trust me, train yourself not to think about it, and it will go away for extended periods of time (and will come back from time to time)