Black Bears have very poor eyesight and have to rely on their' sense of smell and hearing. If you were making very little or no noise and the Bear could not scent you, then it was probably trying to figure out what you both were. It is the Sows with Cubs that you really have to worry about and occasionally a Boar that has been hunted and shot sometime in the past. When the Bears are far enough away and unaware of your presence or unsure as to what you are, then sometimes and I repeat sometimes, you can scream at the top of your' lungs and they will run out of there like a bolt of lightning.
Frank