"The ear is tenuous and has a high demand for blood flow," Rauch said. "Every time you light up a cigarette, you are minimally reducing blood flow to the ear. Over a lifetime of being a smoker, you are suffocating the ear a little bit."
Although one study, published in the Journal of the Association for Research into Otolaryngology, showed that smokers have more difficulty hearing high frequency sounds compared to non-smokers, and that hearing deteriorates after smoking regularly for more than a year.
Toxic noise that leads to mechanical injury in the cochlea is one of the most important factors in hearing loss. But a noisy environment goes hand-in-hand with many occupations.
Musicians, construction workers, factory workers and firemen are some of the people at high risk for constant exposure to loud noise.
"Research indicates that noise injury is a gift that keeps on giving, like a snowball down a hill," said Rauch. "Noise between 70-90 Db does slowly cause increased wear and tear on your hearing... That is a huge implication for occupational impact noise exposure."
Loud noise can cause injury by damaging the hair cells in the cochlea by bending and vibrating in response to sound. Loud sounds force those cells to flex with greater magnitude until eventually they break or wilt and don't respond to noise properly.
"If you beat on those hair cells hard enough they die," Rauch said. "Those cells never regenerate."
Since noise is a dose effect, sudden loud sounds can be just as if not more damaging than prolonged exposure to 80 Db of noise over eight hours in a factory, for example. A gunshot sounding at about 150 Db can do the same amount of damage in a fraction of a second as the accumulated injuries a musician might have, for example, and this can be an issue for war veterans, for example.
Diabetics are at risk for impaired hearing because their blood vessels are abnormal, Rauch said.
"Impairment of blood flow to the ear is bad," Rauch said. "It can go dead, like a stroke."
Narrow or abnormal blood vessels can prevent sufficient blood from reaching the cochlea as well as prevent toxins from getting cleaned out. This has the potential to damage the delicate cells within the ear.
"Diabetics can lose their hearing bit by bit," Rauch said. "It's not sudden deafness."
People with sickle cell anemia suffer from fatigue and pain because their red blood cells -- the vehicles for carrying oxygen and nutrients to cells and taking wastes away -- are misshapen. Such cells cannot transport as much energy to the body as normal blood cells do and their curved shape gives them the dangerous potential to slow down and clot.
Abnormally flowing blood can keep valuable nutrients from reaching cells in the ear.
"The ear has a high metabolic rate, it's active all the time -- you can't turn off ears," Rauch said. "With sickle cell anemia, you get sludging blood flow. A sickler might go deaf or lose their hearing suddenly because of a crisis."
The clanging, grinding, squeaking sound of a subway may be simply annoying to some, but regular riders are at risk for impaired hearing.
The sounds of a train damage the delicate sound machinery inside the ear, and are an example of how loud noises for short periods of time -- when a train is pulling into the platform as well as during a prolonged ride -- can be damaging.