It is pretty common in some people to listen to your heartbeat or a pulse in your ear when lying down in bed. It is medically known as pulsatile tinnitus. Sometimes it is in one ear or sometimes in both. Although it is not something very serious about your health, it can be aggravated if your blood pressure is high. If your blood pressure is normal, it is not a cause of concern. Still, it may be intensified by any increased “catecholamine” release (for example, adrenaline) in situations such as caffeine consumption, anxiety, fear, etc.