A couple of possible answers come to mind. First, there is a large source of blood flow in your head close to the bottom of your ear canal. The carotid artery is large and can sometimes produce a pounding or heartbeat sound in your ears, particularly after exercise or exerting yourself. It is common to have tinnitus (or noises in the ear) on one side instead of both ears. Tinnitus can be a ringing, whistle, roaring or even a pulsing sound. The pulsing sounds more like what you are experiencing.

I would want you to see your primary physician to rule out high blood pressure or other medical conditions as a cause, particularly if you feel your hearing is normal. You may be directed to an audiologist for a hearing test by your primary doctor as part of the work-up. If so, you may be asked questions about how often and for how long your tinnitus occurs. Be sure to document when it happens and if there is anything you are doing at the time, such as exercising.