A ringing or noise in the ear is called tinnitus. This sound can be a ringing, a humming, a buzzing, a swishing, a leaking radiator, a chirping bird, the sound of wind, the sound of rain, the sound of the ocean, crickets. It really doesn't matter what it sounds like. It only matters that it's there.
The only exception to this statement is if the noise is pulsatile, that is to say if it is in rhythm with your heart. If the noise is in rhythm with your heart it suggests a group of vascular problems such as a blockage of an artery in the neck or a vascular tumor perhaps near the ear.
It is unusual for tinnitus to be pulsatile or in rhythm with your heart. Most of the time it's just a constant noise, but its quality and its pitch is very, very variable and is really not significant. The only thing that is significant is that the noise is there, because that means there is something wrong with your ear and that mandates a consultation with an otolaryngologist, an ear, nose, and throat physician, in order to be evaluated.
The types of things that can cause a noise in your ear include a tumor in the ear, usually not malignant, almost always benign, an infection in your ear, or various types of hearing loss. So, it's very important that when this noise arises you seek a consultation, because often, if it is addressed early, it can be cured. But, if it is left and not attended to, after years it might be permanent.
Tinnitus is of particular concern when it is only in one ear. When it's in both ears it generally relates to some underlying age related or genetically determined hearing loss. But when it is only in one ear we are much more concerned about the possibility of an infection or a benign tumor.