Yes, this is exactly my experience has been with my St Jude. I almost never hear it, except when I take a deep breath. I'm sitting quiet at my desk right now and can't hear it at all. I take a very deep breath and I hear about 4 beats- perhaps more accurate to say that I feel them. I also have a dacron sleeve which replaced my aortic root and most of my ascending aorta.
And no one has ever heard my valve unless they put their head on my chest. I participate in Brazilian Jiu Jitsu, which is a grappling martial art. Often we end up in positions with our ear on our opponents chest and on a couple of occasions my training partners have heard it. Most recently a young man looked at me surprised and said: "Dude you're ticking." I explained that it was my mechanical valve. His response was epic: "So, you're Iron Man, cool!" lol