Occupational Hearing Loss

WDC Journal Edition: May 2002
By: Andrew Quartaro - Peterson, Johnson & Murray, SC

Occupational hearing loss claims have proven to be difficult cases to defend. Many employers, insurance adjustors and attorneys are confused by the intricacies of Wis. Stat. § 102.555 and Wis. Admin. Code § DWD 80.25. As a result, there is a poor understanding of occupational hearing loss claims and how to defend against them.

In order to evaluate a worker's hearing loss claim, some background information is needed in regard to the type of hearing loss the worker has. According to the American College of Occupational Medicine Noise and Hearing Conservation Committee, there are certain principal characteristics of occupational noise-induced hearing loss. The primary characteristic of occupational hearing loss is that it is always sensorineural. This type of hearing loss results from damage to the end organ of the inner ear where sound is transmitted via the acoustic nerve to the brain. Newman v. American Motors Corp., LIRC Dec. No. 92-017424 (January 7, 1994).

Sensorineural hearing loss may be caused by prolonged exposure to noise but may also be a natural consequence of aging. Other factors which may contribute to sensorineural hearing loss are the employee's general health (arteriosclerotic disease and diabetes are known to accelerate sensorineural hearing loss in an unpredictable fashion), ototoxic medication, genetics and recreational noise exposure. Unfortunately, an audiogram cannot separate sensorineural loss caused by noise, aging or some other cause. Calderon v. Brand Insulation, Inc., LIRC Dec. No. 95-013880 (April 30, 1996). Sensorineural hearing loss from noise exposure may be temporary or permanent but if hearing has not bounced back from trauma or noise exposure within 14 days, it is usually considered irreparable. 3A Attorneys' Textbook of Medicine, Secs. 84A.60 and 84A.65 (1994).

Sensorineural hearing loss must be distinguished from conductive hearing loss, which is generally associated with blockages in the middle ear or ear canal from wax, blood, bone fragments and the like. See Newman. If hearing loss proves purely conductive, it cannot possibly be related to noise exposure. Id. The only occupational deafness compensable under Wis. Stat. § 102.555 is hearing loss caused by exposure to noise; thus, only sensorineural hearing loss may be compensated under the statute. Id. Conductive hearing loss is not compensable as occupational deafness.

When the hearing loss is mixed; that is, hearing loss attributable to both the conductive hearing loss and sensorineural loss, the numbers from bone conduction audiometry should be used instead of air conduction audiometry. Calderon v. Brand Insulation, Inc., LIRC Dec. No. 95-013880 (April 30, 1996). The Wisconsin Administrative code provides that, for the purposes of determining hearing impairment, "pure tone air conduction audiometry is used" to measure loss over six frequencies. However, compensation is determined by using a formula based on the average measurements at four frequencies: 500Hz, 1000Hz, 2000Hz and 3000Hz. An audiometric measurement at these four frequencies averaging 30dBs or less does not constitute any practical hearing impairment. Wis. Admin. Code § DWD 80.25(4). Although the rule seems to indicate that only numbers from the air conduction audiometry are used to determine occupational hearing loss, that is not the case.

Hearing measurements determined by air conduction audiometry are done through ear phones placed over a subject's ears. See Newman The sound passes from the outer through the middle to the inner ear, so that the hearing loss measured may be caused by disease or injury in one or more of those areas. See Newman, citing 3A Attorneys Textbook of Medicine, Section 84A.81. Bone conduction tests on the other hand, are done by placing a tuning fork or similar vibrator against the bones of the skull. Sound transmitted by bone conduction travels through the cranial bones to the inner ear. Id., citing 3A Attorneys Textbook of Medicine, Section 84A.22. Because it effectively bypasses the outer and middle ear, a measurement done by bone conduction better reveals the status of the inner ear. Id. By using both air conduction and bone conduction tests, a doctor is able to determine the portion or portions of the ear where there is a problem. Id. Thus, in cases where the hearing loss measured by air conduction is worse than that for bone conduction, one can conclude that the bone conduction test shows the actual sensorineural loss and that the additional loss shown by the air conduction test represents conductive hearing loss. Id., citing 3A Attorneys' Textbook of Medicine, Section 84A.200(4).

In addition to being always sensorineural, occupational noise-induced hearing loss is almost always bilateral. Audiometric patterns are usually similar bilaterally. Noise-induced hearing loss almost never produces a profound hearing loss. Usually, low-frequency limits are about 40dB and high-frequency limits about 75 dB. Further, once the exposure to noise is discontinued, there is no significant progression of hearing loss as a result of the noise exposure. In addition, previous noise-induced hearing loss does not make the ear more sensitive to future noise exposure. Moreover, there is always far more loss at 3000, 4000 and 6000 Hz than at 500, 1000, and 2000 Hz. Lastly, continuous noise exposure over the years is more damaging than interrupted exposure to noise, which permits the ear to rest.

The Statute And Code
Wis. Stat. § 102.555 defines "occupational deafness" as permanent partial or permanent total hearing loss in one or both ears due to prolonged exposure to noise in employment. Under Wis. Stat. § 102.555(2), temporary disability benefits are not recoverable. Thus, the only primary benefit recoverable by the applicant is permanent disability benefits. Permanent partial disability for bilateral hearing loss is computed proportionally using a 216 week base for total deafness, while hearing loss in one ear is computed using a 36 week base. Wis. Stat. § 102.555(4). In regard to medical treatment, there is no known medical treatment for hearing loss other than hearing aids. Wis. Admin. Code § 80.25(6).

The are several potential dates of injury in an occupational hearing loss claim. Under Wis. Stat. §102.555(4), the date of injury, at the option of the employee, may be any of the following: (a) transfer to nonnoisy employment by an employer whose employment has caused occupational deafness; (b) retirement; (c) termination of the employer-employee relationship; or (4) layoff, complete and continuous for six months. There is a seven day waiting period after the designated date of injury before an application can be filed. This recognizes the fact that hearing can improve after an absence from noise.

In order to prove an occupational hearing loss claim, the worker must show evidence that he or she was exposed to noisy employment which is usually done through noise level surveys, co-worker testimony or the worker's testimony. Noise means sound capable of producing occupational deafness. Wis. Stat. § 102.555(1). Noisy employment is employment where an employee is subject to noise. Id. Technically, pursuant to Wis. Stat. § 102.555(7), there must be at least 90 days of exposure to noisy employment; in general, however, it takes several years for such exposure to create a hearing loss.

In determining whether an employee has been subject to harmful noise several factors are considered including the overall intensity (sound pressure level), the daily exposure, the frequency characteristic of the noise spectrum and the total lifetime exposure. Wis. Admin. Code § DWD 80.25(1). Pursuant to that code section, "[n]oise exposure level of 90 decibels or more as measured on the A scale of a sound level meter for 8 hours a day is considered to be harmful." This code section, which is generally the standard established by OSHA, creates a presumption that noise exposure in excess of 90dBs per eight hour day can cause hearing loss. Kimberly-Clark Corp. v. LIRC, 138 Wis. 2d 58, 405 N.W.2d 684 (Ct. App. 1987). However, hearing loss can still result from exposure to less than 90dBs. Id. The worker must also show that he or she has sufficient hearing loss. Under Wis. Admin. Code § DWD 80.25, only hearing loss that rates out between 30dB and 93dB is compensated. Each decibel of loss in that range is compensated by a 1.6 percent impairment rating, applied to the 36 week or 216 week base. Wis. Admin. Code § DWD 80.25(8). The Department has concluded that losing the ability to hear between 0 and 30dB is not an impairment from a real world perspective and that losing additional decibels beyond 93 decibels is not a compensable impairment because, by the time the person has lost the first 93 decibels, he or she is deaf for all practical occupational purposes.

In determining hearing impairment, the average of the 4 speech frequencies of 500, 1000, 2000 and 3000 is used. Wis. Admin. Code § 80.25(4). No deduction is made for sensorineural loss due to age. Id.

An employer is generally liable for all the occupational deafness to which his or her employment contributed. Wis. Stat. § 102.555(8) However, if the employer can prove pre-employment deafness, even pre-employment occupational loss, it does not have to pay for the loss from pre-existing loss. Wis. Stat. §§ 102.555(1) and (8). However, employers only receive a credit if an employee begins the employment with hearing loss greater than 30 decibels. Harnischfeger Corp. v. LIRC, 196 Wis. 2d 650, 539 N.W.2d 98 (1995). Thus, one successful defense to a hearing loss claim is proof that the employee had a hearing loss predating his or her employment with that employer. For this reason, it is a good idea for employers to require routine "pre-employment audiograms." Where no such audiograms are available, the employer may become liable for the worker's entire hearing loss. If there is pre-employment deafness which is due to occupational disease from employment with another employer, and the worker is barred from proceeding against the other employer by the statute of limitations, the worker may be entitled to a recovery from the work injury supplemental benefit fund pursuant to Wis. Stat. § 102.66.

Defending Against The Claim--The Employer
Employers can help with noise-induced hearing loss claims such as redesign or replacement of old equipment, installation of sound absorption or attenuating materials, relocation of noisy equipment, equipment repair or changes in maintenance procedure. If such changes are not feasible economically, then the employer should modify work schedules to reduce the length of noise exposure or change the times for equipment operation, or issue personal hearing protectors. Whatever method is used, the goal is to reduce the noise exposure level to 90dBs or lower for every eight hour day. Further, a baseline audiogram should be obtained when the employee is hired and an exit audiogram should be performed when the employment is terminated.

Further, under Wis. Admin. Code § 11.04, an employer has the duty to conduct noise surveys and to keep the results of such surveys on file. If such tests are available and are not produced at hearing, the inference will be that the results were unfavorable to the employer. Rexnord Corp. v. DILHR, 105 Wis. 2d 763, 318 N.W.2d 23 (Unpublished Ct. App. 1981). The worker does not have the obligation to produce evidence of decibel levels. Id.

Defending Against The Claim--The Insurance Carrier
In a hearing loss case, it is essential to know the exact period of employment. The worker must prove a prolonged period of work place exposure causing hearing loss. A medical opinion is not needed if there is evidence that the worker was not exposed to noisy employment. The insurance adjustor should find out when the applicant began working for the employer, when the worker's employment ended, were any noise level surveys performed, were any audiograms required, how many hours per day/week were worked, the place where the worker did most of his or her work, how much time was spent in each department if the worker did not spend all of their time in one department, was the noise daily, was the noise constant, did the noise vary in frequency, names of co-workers, was hearing protection provided and the machines/tools used. The employer could prove that the worker was not exposed to harmful noise by having noise level surveys which show less than harmful noise, testimony from co-workers that it was not necessary to shout when carrying on a conversation or proof that the worker was required to wear hearing protection at all times. If hearing protection was provided and their use was enforced, the worker could have benefits reduced 15% under Wis. Stat. § 102.58 if the worker did not use the aids.

The insurance adjustor should gather all medical and employment records to determine if there are any pre or post employment audiograms. If there is an audiogram establishing hearing loss shortly after the date of injury and another audiogram establishing hearing loss after that time, the earlier audiogram will be used to compute hearing loss unless there is a medical opinion relating the increased hearing loss to the prior occupational exposure. See Calderon The medical records may also reveal other potential causes for the worker's hearing loss such as deerhunting or woodworking. A recorded statement should also be taken, if allowed, to determine other potential causes. If the worker was in the military, those records should also be requested. Lastly, an IME with an otolaryngologist should be considered to question the hearing impairment. Because most workers can establish causation, most cases involve a dispute over the degree of hearing impairment (demonstrated by two audiograms with different assessments of hearing impairment) rather than a dispute over causation.

Conclusion
Occupational noise-induced hearing loss, as opposed to occupational acoustic trauma, is a slowly developing hearing loss over a long period (several years) as the result of exposure to continuous or intermittent loud noise. A worker claiming occupational hearing loss establishes a prima facie case once he or she demonstrates that he or she has sustained a sensorineural hearing loss and that there was exposure to prolonged harmful noise. The worker must provide a valid audiogram indicating an average decibel hearing loss greater than 30dBs and that the sensorineural hearing loss was caused by exposure to hazardous noise. To successfully defend a hearing loss claim, the employer must establish that the worker had a hearing loss pre-dating his or her employment; that the worker was not exposed to hazardous noise; that the hearing loss was caused by some other reason such as age, ototoxic drugs, military, hobbies, etc, or that the degree of impairment as alleged by the worker is not accurate.