While it's generally regarded as good parenting to monitor the kind of music your child is listening to, knowing the song that's blasting in your child's headphones just by standing next to him or her is probably not the best way to find out.
But beyond tuning out the world and turning up the jams, there are a several ways people may prematurely damage or lose part or all of their hearing before age or genetics do it.
The following is a list of ways hearing can be damaged and lost.
"Our ears really weren't meant to listen to music at the level we're listening to it for hours and hours," said Dr. Geroge Alexiades, an otologist and neuro-otologist at the New York Eye and Ear Infirmary.
But Alexiades pointed out that the problem is not necessarily having music playing so close to the ear but when that music is played loudly to drown out other sounds using ear buds that were not made to plug the ear canal.
"With ear buds that don't block background sound, people crank up their music louder," Alexiades said. "The intensity of sound we can listen to depends on how long we can listen to it."
Using ear buds can also show how hearing can change after long exposure to certain noise levels. Eventually, our ears undergo a temporary threshold shift, when our perception of normal volume changes and it is difficult to hear softer noises -- after a rock concert, for example.
The effect, however, is usually temporary and hearing will return to normal within several hours if no lasting damage was done.
While ear buds plug the ear canal and block ambient noise so that music may be played at a lower level, doctors caution that this can be dangerous in situations where noise cues are important for safety -- while driving or walking on a street, for example.
"The more you [drive], the more chance you have of developing permanent problems," said Dr. Philip Michael, an ear, nose and throat surgeon at Queen Elizabeth Hospital, in Birmingham, England, who presented his findings at the October meeting of the American Academy of Otolaryngology. "It's a cumulative risk."
"There's a humanitarian reason for [this research] but also another reason, which is that I like cars," said Michael, who drives an Audi convertible.
But Michael's findings revealed more than personal taste. Measuring the sound a driver will hear in several types of convertibles, including a Toyota MR2, an Aston Martin V-8 Vantage, and a Porsche 997 Carrera, at speeds between 50-70 miles per hour, Michael found that drivers are exposed to noise levels of 88-90 Decibels (Db).
The average conversation is held at about 50 Db, street traffic is about 70 Db, and an operating lawnmower is about 90 Db. Repeated exposure to over 85 Db is known to cause permanent hearing loss.
Greg Fletcher, 49, of Orange County, California, has owned a vintage Jensen Healey convertible since 1985, and said he is all too aware that convertibles are not the peaceful joy ride of people's fantasies.
"A convertible is something pleasant to drive on country roads at 40 mph," Fletcher said. "But [in my car] there's not much insulation, the engine is noisy, it vibrates a lot... Even with the top up I can't talk on the phone."
But the noise of the car is not the primary problem, Michael said. Wind noise at high speeds and traffic noise as lower speeds are worse.
"When you've got a truck next to you, it's deafening," Fletcher agreed. "It's the most awful thing, and you just want to get away as quick as you can."
Although Fletcher is not sure that driving his convertible several days each week will cause deafness, he said many owners know a convertible is not the best way to protect hearing.
"It's hard to say. I don't think my hearing is quite as good as it used to be," Fletcher said. "It hasn't gotten to a point where it's interfering with my daily life. But it's probably contributed in a negative way over the years."
One of the lesser-known side effects of several types of drugs, including pain medications, certain antibiotics and platinum-based chemotherapy drugs, is hearing loss.
A three-year Vicodin addiction left Shannon Menosky, 40, from Riverside, Calif., deaf. Her habit, which at its peak was 50 pills a day, gradually killed the delicate hair cells in her inner ear until, after a month of deteriorating hearing, Menosky woke up to total silence.
"It was kind of gradual," said Menosky. She first noticed that it was difficult to talk on the phone, that her children had to shout to get her attention and that she had to turn up the volume on the television. "And then I woke up one morning and there was literally nothing," Menosky said.
Her doctors at the House Ear Institute in Los Angeles said her hearing loss was permanent and would require a cochlear implant to restore it. Menosky said she broke down.
"Once I lost my hearing, I think I started taking Vicodin more," Menosky said. "I wouldn't leave the house. I was depressed that I couldn't hear my children or my family."
Medications that are ototoxic have chemical properties that make them toxic to the sensory cells in the ear.
Classes of drugs famous for this side effect include strong aminoglycoside antibiotics that are used in cases of life-threatening infections, such as a bone infection.
"These cause irreversible deafness," said Dr. Steven D. Rauch, professor of otology and laryngology at Harvard Medical School and the Massachusetts Eye and Ear Infirmary. It can be very rapid, very quick and very permanent."
Strong pain medications like Vicodin and oxycontin can kill inner ear cells, but over-the-counter pain medications such as ibuprofen and aspirin can also cause hearing loss to a lesser degree. High doses of mild pain medication may cause ringing in the ears before it begins to affect actual hearing and will go away after discontinuing use.
Platinum-based chemotherapy drugs are another class of ototoxic drugs because heavy metals build up on the hair cells and poison them.
While the lungs and heart take the brunt of damage from smoking, the ears can be affected as well.
One blood vessel serves the cochlea, the sense organ of the inner ear, and restricting blood flow can prevent enough oxygen from reaching it.
Nicotine, a vasoconstrictor that causes blood vessels to shrink slightly, can have a profound effect on the small capillaries that serve the ear.
"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."
Sickle Cell Anemia
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.
And while subway workers may be aware of the noise damage and protect their ears accordingly, riders are less likely to do so.
Alexiades pointed out that the Union Square subway station in New York City is particularly noisy.
"With the curved tracks, you get a lot of squealing," he said.