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Occupational Noise Exposure

Introduction:

Noise at the workplace is one of the most common hazards for the American workers today. The worst part of it is that loss in hearing due to noise exposure is difficult to notice because it grows slowly and painlessly and causes the disability before one can notice it. The workforce mostly exposed to noise is the construction worker. According to an estimate one quarter of the five million construction workers in the US are exposed to average daily noise levels above 85 dBA (considered unsafe for 8 or more hours per day) (Lusk). There is a strong need of reducing noise exposure by implementing different engineering controls.

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Hearing loss due to noise exposure at work affects approximately 28 million people in the United States. According to an estimate about 10 million of these deficiencies are caused because of the damage from exposure to loud sounds. Any kind of noise or large sound have a capacity to damage the structure of ear and as a result can produce loss of hearing which is at least presently not curable through any medical treatment. There is no age limit for the disability in hearing, it can occur at any age even in early childhood. Loud sounds of shorter duration are of more severe effects and can even cause permanent loss of hearing. However, exposure to less severe sound for longer periods of time, as is the situation in the workplace, can cause a gradual decrease in the hearing ability of an individual. The considerable factor in this regard is that the particular individual experiencing loss of hearing due to exposure of less intense noise cannot notice the damage. A majority of American workers are exposed daily to hazardous noise levels that can cause a permanent disability to them. The most common cause of noise-induced hearing is occupational noise exposure that endangers the hearing capability of workers. There are some other non-occupational sources of noise exposure as well that include live or recorded high-volume music, recreational vehicles, airplanes and household appliances. One considerable factor of Occupational Noise exposure is that it is preventable in all but certain cases of accidental exposure. The government has passed several legislation and regulations defining the rules and guidelines to protect workers from hazardous noise levels in the workplace. It also defines the guidelines to protect the consumers from hazardous noise during leisure time activities.

Effects of Occupational Noise Exposure:

The human ears are very subtle and complex organism. Damage is very easily caused to the ears because of their delicacy. They can hear loss if any part of the structure is not working. Loss of hearing is defined in two separate categories on the basis of the deficiency in functionality of a particular part of the ear. They are named as conducive and sensorineural. The cause of conducive hear loss is any obstruction caused to the transmission of sound in the outer or middle ear. On the other the reason for the sensorineural loss is the deficiency in the functionality of the inner ear. The hear loss caused to any individual can be conducive and both as well. The loss of hearing can be minor as well as it can cause total deafness. The level of hearing deficiency can be determined through hearing tests.
The exposure to occupational noise can cause loss of hearing that is defined in two different categories namely temporary threshold shift and permanent threshold shift. The most frequently experienced loss of hearing is the temporary threshold shift. It is a temporary deficiency of hearing caused by exposure to loud noises. The hearing ability will be recovered but this recovery depends on the loudness of the sound and the length of time an individual was exposed to noise. On the other hand, permanent threshold shift is the damaged caused to the hearing capabilities of a person’s ear permanently. A hear loss is considered permanent if it is not recovered with in 48 hours of exposure to the noise. Permanent threshold shift is further classified into two more categories. One is noise-induced hearing loss and the other is acoustic trauma. The noise-induced hearing loss is caused because of the usual exposure to hazardous noise levels for a long duration. The individual acquires a hear loss n regular basis which affects more severely to the hearing ability of a person as compared to the damage caused by high frequencies of sound. The causes of an acoustic trauma are the exposure of an individual to a sound of very high frequency level for a short span of time. Such high frequency sounds can cause a sudden damage to the hearing ability of a person and severely affects the hearing. In such cases, usually a sensorineural hear loss is experienced but sometimes a very strong level of sound can permanently damage the ear. For a person suffering from hearing loss caused by occupational noise exposure, tests usually have shown the hearing loss to have a distinctive pattern. This pattern indicates a plunge in an individual’s hearing capabilities at very high frequencies i.e. around 3-4 kHz. If the exposure to noise to an individual continues, the audiogram (a chart indicting a person’s hearing levels when he/she goes through a hearing test) will also show this affect in lower and higher frequencies too. This loss of hearing will continue to grow for a long period of time and will cease to become more worst at a point until and unless the individual is further exposed to some sort of noise. In the beginning it is usually difficult to notice the loss of hearing and people usually do not realize any such damage. However, when it spreads and start affecting an individual’s hearing capabilities for large frequencies as well, then people notice the damage. In such case an individual may face difficulty in following conversations if there is background noise. In case of acoustic trauma, individuals usually find difficulty in hearing from one ear, depending upon the seriousness of the loss caused to the hearing ability of that ear. A person may not face many problems in hearing during conversations because the ear that is unaffected from the loss is able to receive the sound in normal fashion. However, person’s experiencing this kind of hear loss is going to feel that the sound he/she is hearing is unclear and that the speech is deadened. The primary reason for such problems are the loss of hearing ability to detect high frequency sounds.

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Noise exposure not only causes hear loss but it may lead to some other deficiencies as well. One of such problems caused because of noise exposure is ringing sounds in ears or head or other similar kind of noises. This problem is caused primarily because of frequent exposure to noise and this may occur without any obvious loss of hearing. In some cases individuals suffers from an inability to hear quite sounds but hears loud sounds pretty well. An individual’s hearing starts to get affected when he or she is exposed to more than a unsafe amount of noise. The hazardous noise level varies a lot from person to person and such factors as age, previous noise exposure and genetic susceptibility contribute to an individual’s ability to tolerate to a particular noise level. The general for noise’s effect is that the higher the intensity of the longer it continues to have it’s affect and the more likely it is to damage hearing.

Measuring Occupational Noise:

There is no single standard procedure or method for measuring occupational noise. A wide range of instruments can be used for the measurement of noise and there are a number of instruments and software available for the analysis of these measurements. The decision to chose a particular instrument and procedure of measurement and analysis of occupational noise can be based on a number of factors including the purpose for the measurement and the environment in which the measurement will be made. The methods for measuring noise, adopted by any organization should be in conformance to American National Standard Measurement of Occupational Noise Exposure, ANSI S12.19-1997 [ANSI 1996a]. The most commonly used instruments for measuring noise exposure are the sound level meter and the noise dosimeter. The sound level meter is a basic instrument used for measuring noise exposure. It has a microphone, an amplifier for frequency selection and an indicator. 

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It is the responsibility of the employer to establish and maintain an audiometric testing program. This program should be accessible to all employees who are exposed to the sound level that is considered hazardous. The employer should provide this program to its employees for free.  Sound level meter is the most feasible equipment for measuring noise in conditions where there is continuous exposure to high level noises and where workers are supposed to work in a limited position during their working hour. In case of varying noise levels and workers frequently changing their positions, it is better to use a noise dosimeter.

Reducing Noise Levels:

While defining ways to reduce noise several steps can be taken. One can look at ways to replace or modify equipment, processes or materials and at ways to reduce vibration. A company can also establish a maintenance program for checking the equipments for repair and replacements on the regular basis. Moreover, the company should try to implement a policy of purchasing those equipments that are believed to generate minimum level of sound. Several other measures to control noise at the workplace may include: enclosing the worker, changing the work schedule or operations to reduce workers’ noise exposure such as conducting a noisy operation over a period of a week, rather than one day, transferring workers from noisy jobs to jobs which are exposed to lesser noise levels, but not at the expense of exposing more workers to hazardous noise levels, providing quiet areas where workers can gain relief from workplace noise. Building an enclosure around the worker, such as a control booth, can reduce the noise exposure of a worker. These sound proof booths will prevent the workers from hazardous noise levels even though the noise level of the machine remains the same. These booths must be completely packed and sealed so that it may become safer from outside noise. The devices used for protecting a person from noise usually called the Hearing protection devices (HPD) can also be used for noise reduction. However, they are not a very favorable option and should be avoided if possible. The reason for not giving HPDs primary importance is that it is not easy to select, use and care of these devices. It is also a very time consuming and pretty disturbing job to properly wear these devices. That is why it is more preferable to assure that there is no noise problem at work. The most feasible policy for a company is to implement engineering and administrative controls that will help in reducing the level of noise exposure at work such as purchasing less noisy equipments or modifying the production processes. Hence, the best way to reduce risk to worker’s hearing from noise exposure will always be to reduce noise levels at source. If a company is successful in reducing exposure to noise with respect to time spent in a noisy environment or sound level, the risk of damage to workers hearing will decrease too. Though an employer can implement several steps to reduce noise at work, a small percentage of people will still experience minor hearing loss if they are exposed to some sort of noise over a number of years, so there is always a possibility of some damage to individual’s hearing. The best prevention is for employers to make every effort to reduce the noise at source.

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The OSHA Standards for occupational noise exposure:

Occupational Safety and Health Administration, Department of Labor has defined guidelines concerning the safety of workers from high-level noise. It directs an employer to implement noise safety procedures to prevent employees from hazardous sound levels. It gives preference to the implementation of feasible engineering and administrative controls in order to reduce sounds. If such controls are not effective enough then it recommends the use of personal protective devices. It requires an employer to develop and administer a monitoring program when an employee’s exposure to noise exceeds to 8 hours time with a weighted average sound level of 85 decibels. It also proposes to conduct a hearing conservation programs in such cases. Moreover, it dictates that the equipment used for noise measurement should be working at the maximum level of accuracy. It proposes the monitoring of noise exposure to be repeated on a timely basis especially when there is a change in production, process, equipment or controls increases noise exposures to the extent that additional employees may be exposed at or above the action level or the attenuation provided by hearing protectors being used by employees may be rendered inadequate to meet the requirements of such changes. The regulation also requires the employer to provide audiometric testing and should make them available to the employees free of cost. It also dictates that audiometric testing should be performed by a licensed or certified audiologist, or any other physician, or by a technician who is certified by the Council of Accreditation in Occupational Hearing Conservation, or who has satisfactorily demonstrated competence in administering audiometric examinations, obtaining valid audiograms, and properly using, maintaining and checking calibration and proper functioning of the audiometers being used. A technician who operates microprocessor audiometers does not need to be certified. A technician who performs audiometric tests must be responsible to an audiologist, or physician. (OSHA)

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Works Cited

Occupational Noise Exposure: Regulations (OSHA): from the World Wide Web: http://www.oshaslc.gov/OshStd_data/1910_0095.html

OSHA Standards Abstract: OSHA Standard 1910.95: from the World Wide Web: http://www.cdc.gov/niosh/nasd/docs/oa02100.html

Dr, Sally Lusk: Effects of Occupational Noise: from the World Wide Web: http://www.cdc.gov/niosh/nasd/docs/oa02100.html

What is Noise Induced Hearing Loss?: from the World Wide Web: http://www.cdc.gov/niosh/nasd/docs/oa02100.html

Occupational Noise-Induced Hearing Loss: American College of Occupational and environmental medicine: from the World Wide Web: http://www.acoem.org/paprguid/papers/nihl.htm 

Noise and Hearing Loss: National Institutes of Health Consensus Development Conference Statement: from the World Wide Web: http://text.nlm.nih.gov/nih/cdc/www/76txt.html

Noise Induced Hearing Loss: from the World Wide Web: http://www.occupationalhearingloss.com/noise_induced_hearing_loss.htm
 
 


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