America began as a quiet and serene society over one hundred years ago. That would soon change with the birth of the Industrial Revolution. Thunderous noise encompassed the once silent Northern American towns. Shops and factories roared with noise. Many workstations today linger on in a poor state of aging grace. Ancient machines and antique production lines add to the extreme loud working conditions that have severe effects on the workers. Today's work force is laboring in the noisiest work environment ever. Pollution control and environmental protection measures give the future hope. The annoyance of noise is becoming an enormous problem that can no longer be ignored.
Thirty-five percent of the 28 million cases of hearing loss in the United States are attributable to noise exposure.  Noise causes a difference in auditory sensitivity of 2-8 kHz, which reduces the dynamic range of hearing and impairment of the ability to selectively detect a specific frequency of signal. Pitch distortion, speech impairment, and tinnitus are also signs of sensitivity.  Molecular alterations may precede detectable structural and physiological changes. Hearing loss is insidious, slow, virulent, irreversible and isolating.  "Noise is one of the most common causes of hearing loss, a condition that can have far-reaching psychological and social effects."  Many people with hearing loss become socially isolated because communicating is so frustrating. Their productivity on the job may suffer, and they are at risk of injury if they can't hear warning sounds. Some people with hearing loss often suffer from depression. Hearing loss currently is not completely curable, but it is preventable through common sense measures.
The following are conditions that attribute to hearing damage: 
Signs of hearing loss include: a ringing in the ears and a muffling of sounds. These symptoms stop as the hair cells recover within twelve and eighteen hours, but the hair cells lose their resilience if damaged again and again.  "It's possible for a single, intense loud noise to cause sudden, permanent hearing loss. A sound does not have to be unpleasant to cause hearing loss."  The sounds from enjoyable activities such as listening to amplified music or snowmobiling are just as harmful to the ears as the noise from jackhammers, jet planes, and factory machinery. Conductive hearing loss occurs when sound waves cannot be transmitted from the outer ear to the inner ear.  Common causes include a buildup of earwax in the car canal, a perforated eardrum, or an ear infection. Sensorineural hearing loss (sometimes called 'nerve deafness') occurs when tiny hair cells in the inner ear are damaged.  Normally, these cells are stimulated by sound waves. They generate electrical impulses that are transmitted to the brain through the auditory nerve.
Noise is a health hazard and can affect employee productivity and morale. " Noise is a patient pollutant whose crippling effects aren't often noticed until it's too late. "  Prolonged exposures to noise above 85 decibels can cause a variety of ailments. The following could occur: blood constriction to internal organs, hearing loss, seizures among epileptics, damage to the nervous system which controls the heart and other major muscles, could also harm unborn children, high blood pressure, lack of sleep, possibly heart disease, indigestion, and ulcers. 
Ears are shaped like funnels to collect sound. As the sound travels down the ear canal, it causes the eardrum to vibrate. These vibrations in turn travel to the three bones in the middle ear - the malleus, incus and stapes.  "The stapes footplate transmits these sounds into the fluids of the cochlea, where three outer sets and one inner set of hair cells bend in response and create a charge that stimulates the nerve endings on the bottom of each cell. That is the signal that the auditory nerve carries up to the rain and cortex, which decodes the noise into what we recognize as the cry of a baby, the lunch whistle or the music on the radio."  The cochlea's nerve cells burn out with repeated stress. Genetics is also needs to be considered when determining how fast hearing erodes.
Six hundred million people work in potentially hazardous noisy places.  Environmental and leisure-activity noise is increasingly contributing to acquired hearing loss. The probability of such impairment increases if noise exposure is combined with other factors such as chemicals, extreme temperatures, and vibration.  There is research that shows when combined with ototoxic chemicals, noise levels within current exposure limits can result in hearing loss.  Two excessive exposure to noise damages the cochlear structures in the ear through direct mechanical damage or metabolic overload due to overstimulation. For mechanical damage, repair is unlikely, but there is some potential for phatamacological strategies to counter or reverse metabolic effects. 
The measurement tool is the decibel. Decibels measure the intensity (or amount of energy) produced by sounds, an indication of loudness.  Continuous exposure to sounds over eighty-five decibels is a set-up for future hearing problems. One organization called HEAR (Hearing Education and Awareness for Rockers) is dedicated to raising awareness about hearing loss caused by deafening music. Rockers like Metallica, Red Hot Chili Peppers, Sonic Youth support HEAR's campaign to turn down the amps. Their own agenda is simple: "If the music is too loud, turn it down!"  Rockers have began to wear ear plugs and also want their fans to do the same. Write the following address for a free pair of neon earplugs before you go to the next concert. 
Hearing is Priceless
House Ear Institute
2100 W. Third St., 5th floor
Los Angeles, CA 90057
Related Article: How Loud is Loud
The danger factor of a sound depends on its intensity and duration. Only an hour of exposure to blaring tunes may kill thousands of hair cells, but will most likely bounce back and so will your hearing.  "A single explosive blast louder than 160 decibels - such as the crack of a shotgun at close range - can instantly kill the sensitive sound detectors by splitting open the membranes on which they sit."  Noise destroys delicate, bristly cells that line the snail-shaped chamber of the inner ear, or cochlea.  These hair cells are responsible for translating incoming sound waves into electrical impulses, the language of the brain. 
Common sense measures can be taken to ensure that you do not damage your hearing while on the job. Avoid loud noise environments whenever possible. Always wear hearing protection around such areas, which can provide a 30 dB noise reduction.  However, there is a downside for earplugs. They make communication between workers difficult. Take time away from the loud work areas during a shift with exposure to continuous noise gives your ears a small break.
"The Noise Control Act of 1972 empowers the Environmental Protection Agency to determine the limits of noise required to protect public health and welfare; to set noise emission standards for major sources of noise in the environment, including transportation equipment and facilities, construction equipment, and electrical machinery; and to recommend regulations for controlling aircraft noise and sonic booms."  The law further requires that consumer goods be labeled with their noise-generating characteristics so that buyers may select quieter equipment.  However, noise control is not being taken seriously by companies. Supervisors and employees must take a stand on their own to protect their ears.
Hearing loss can be an indicator of a more serious problem, it should never be ignored. A doctor should be consulted to rule out medical causes for the problem. In some cases, relief can be obtained immediately. Removing a buildup of earwax is sometimes all that is needed to restore hearing. No surgical or medical treatment can undo the damage caused by noise, but hearing aids can sometimes restore some degree of hearing.
A "noise control pill" to limit noise-induced hearing damage may be only a few years away. "Commission Concerted Action for Protection Against Noise (PAN) proposed several new ways of manipulating the cochlea's own endogenous protective mechanisms to safeguard it against the kind of excitotoxic damage that affects four hundred to five hundred million people worldwide."  The cure seems to be in limiting noise damage to the outer and inner hair cells of the ear and even to the spiral ganglion and auditory nerve by giving or upregulating neurotropins, growth factors, heat-shock proteins or free-radical scavengers. 
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