It's probably physical or neurological caused by stress. I agree with Amanda it's probably something in your ears. I hear a sound resembling a sound of boiling water from time to time. It's from frequent ear infections as a child. I'm used to it and I don't even think about it. It can also be from high blood pressure caused by stress. Or an echo of your own heart which gets worse in stress. Since you've had it for such a long time it probably isn't serious but you can contact your ENT or neurologist to check it out.