Noise exposure. Exposure to loud noises can damage the outer hair cells, which are part of the inner ear. These hair cells do not grow back once they are damaged. Even short exposure to very loud sounds, such as gunfire, can be damaging to the ears and cause permanent hearing loss. Long periods of exposure to moderately loud sounds, such as factory noise or music played through earphones, can result in just as much damage to the inner ear, with permanent hearing loss and tinnitus. Listening to moderately loud sounds for hours at a young age carries a high risk of developing hearing loss and tinnitus later in life.
Tinnitus might also get worse with age and is most common among older adults who suffer from general hearing loss. Some 27 percent of older and elderly adults report having tinnitus, many of them seemingly due to factors like loud workplaces. (9) The elderly commonly experience tinnitus and hearing loss due to symptoms associated with circulatory problems, inflammation and nerve damage.
Tinnitus is the perception of sound when no actual external noise or sound is present. It is often referred to as “ringing” in the ears. I have even heard some people call it “head noises.” While ringing sounds are very common, many people will describe the sound they hear as buzzing, hissing, whistling, swooshing, and clicking. In some rare cases, tinnitus patients report hearing music. I hear about 2,000 crickets all going at once! 
While there may be a wide range of causes, an important underlying factor for the development of tinnitus is brain plasticity.5,7 This property allows the brain to change and adapt, and it is essential to how we learn. Unfortunately, in some cases, such as with hearing loss, the auditory part of the brain may be altered as brain plasticity tries to compensate for the abnormal auditory inputs. This response leads to changes in brain activity in the auditory system (e.g., the auditory cortex) that can create a phantom percept: tinnitus. As such, while tinnitus may begin a problem at the auditory periphery, it persists because of changes throughout the auditory system. Treating tinnitus may require addressing both the initiator (e.g., hearing loss) and the driver (changes in the auditory brain).
Paquette et al (2017) reported a prospective study of 166 patients who had brain surgery involving removal of the medial temporal lobe. The prevalence of tinnitus increased from approximately from 10 to 20% post surgery. This study did not include a control -- a natural question would be -- suppose a different part of the brain were removed. One would also think that drilling of the skull from any source might increase tinnitus. We are presently dubious that the medial temporal lobe suppresses tinnitus.
Atherosclerosis. With age and buildup of cholesterol and other deposits, major blood vessels close to your middle and inner ear lose some of their elasticity — the ability to flex or expand slightly with each heartbeat. That causes blood flow to become more forceful, making it easier for your ear to detect the beats. You can generally hear this type of tinnitus in both ears.