The employee appeals from the compensation judge’s determination that she sustained neither an occupational disease nor a Gillette injury^[1] in the nature of an aggravation or acceleration of her right ear hearing loss arising out of and in the course of her employment with the employer.  We affirm.

Heather Moon, the employee, was initially employed as a quality control person in the imaging department of the self-insured employer, Travel Tags, Inc., beginning on September 8, 2004.  She became a machine operator in the imaging department in 2008.  A pre-employment examination on August 31, 2004, noted bilateral hearing loss since birth and early youth.  A September 22-23, 2004, noise dosage study of the employer’s work environment, conducted by Pinnacle Engineering, established the employer did not exceed OSHA’s 90 decibel permissible exposure limit over an 8-hour time-weighted average.  However the employer did exceed the Hearing Conservation Act’s 85 decibel action level in four out of five of the employer’s departments, with the exception of the imaging department.  As a result, the employer was required to establish a noise exposure program including audiometric testing of employees and ear protection to employees who requested it.  The employee initially elected not to use hearing protection, and after 2008, was excepted from mandatory use, as she was unable to communicate with her co-workers while using hearing protection.

The employee’s pediatric medical records document numerous, recurrent ear infections and other ear problems dating back to 1978, the year of her birth.  In 1982, when the employee was four years old, a small hearing deficit was noted at school.  Audiometric testing in April 1982 showed a bilateral mixed hearing loss, more pronounced on the left, with both conductive and sensorineural components.^[2]  Dr. Leighton Siegel, an ear, nose and throat specialist (ENT/otolaryngologist), recommended the insertion of tubes.

An audiogram on March 7, 1983, showed a moderate low frequency hearing loss sloping to severe high frequency hearing loss in the left ear, and a mild (40 dB at 250 Hz) sloping to moderate (55 dB at 2000 Hz) mixed hearing loss in the right ear.  The employee returned to the clinic for a trial hearing aid in the left ear in May 1983.  In January 1984, the employee’s pediatric physician noted the employee had hearing aids in both ears and there was a large hole in the left ear where the tube fell out.

In October 1984, Dr. Siegel performed surgery on the left ear to repair the hole in the tympanic membrane.  The employee’s hearing continued to worsen, particularly in the left ear, and audiometric evaluation in February 1986 showed a severe to profound mixed hearing loss in the left ear with a mild sloping to severe sensorineural hearing loss in the right ear.  Dr. Siegel performed a second left ear surgery in March 1986, in an attempt to improve the employee’s hearing in that ear.  The employee’s medical records and the employee’s testimony confirm that she had no useful hearing in her left ear after this surgery.

The employee was seen for a follow-up hearing evaluation in August 1988.  Testing indicated the employee’s right ear hearing thresholds were approximately 10 to 20 decibels worse than her previous test results.  Continued monitoring and an audiometric re-check were recommended.  Of note during this period is an addendum to the employee’s pediatric physician’s chart note in October 1990, observing the employee’s brother had also developed a sensorineural hearing deficit.

An audiology recheck and hearing aid check were performed in December 1992.  The audiologist noted no change in hearing sensitivity in the low frequencies, but stated that hearing in the mid-to-high frequencies had worsened 5 to 15 decibels.  The employee was to return in three months to monitor any possible progression.

In 1993, when the employee was 15 years old, she was seen in the pediatrics department stating she couldn’t hear the telephone anymore.  Audiometric testing on October 21, 1993, showed significant hearing loss in the mid- to high frequencies, sloping from a mild hearing loss in the low frequencies to severe hearing loss in the high frequencies.

The employee’s medical records document occasional ear infections, impacted ear wax (cerumen), and eustachian tube dysfunction as an adult.  On January 27, 2004, the employee had an audiology examination at Associated Hearing.  The audiogram showed a progressive decrease in the employee’s hearing thresholds sloping from a moderate (40-55 Db) hearing loss in the lower frequencies to a severe-profound (80-95 dB) hearing loss in the higher frequencies.

Audiometric tests conducted by the employer between September 2004 and 2011 showed a progressive decline in the employee’s hearing in the right ear at all frequencies.  In 2008, the reviewing audiologist, Dr. Sandra Peck, observed the employee’s standard hearing threshold had shifted by 13 decibels on the right.  Dr. Peck opined the hearing loss was not consistent with long-term noise exposure and was not work-related or significantly aggravated by occupational noise exposure.  Dr. Peck again noted a threshold shift of 12 decibels in August 2010, concluding the hearing loss was not work-related based on the employee’s health history, noise exposure readings, hearing test, and pattern of hearing loss.

In September 2011, the employee was seen at Soundpoint [Pindrop] Audiology and Hearing for replacement of a broken hearing aid.  An audiogram indicated the employee had profound hearing loss at all frequencies.  In comparing the results of her audiograms in 2007 and 2011, the audiologist explained she had lost considerable hearing in her right ear.  The employee questioned the employer about noise exposure at work and that led to a report of a workers’ compensation injury in February 2012.

In March 2012, the employee sought further evaluation at her family clinic.  An audiogram on March 21, 2012, showed severe to profound hearing loss in the right ear.  The employee was seen by Dr. Christopher Hilton, an ENT/otolaryngologist, following the audiogram.  Dr. Hilton diagnosed a sensorineural hearing loss.  The doctor instructed the employee to wear hearing protection on the job and stated she should not be exposed to sounds louder than 80 decibels for more than eight hours.  The employee began wearing ear protection at work at about this time.

On March 15, 2013, the employee was seen by Dr. Oleg Froymovich, at Paparella Ear Head & Neck Institute, for additional evaluation of her hearing loss.  Dr. Froymovich concluded that hearing aids would not really improve the employee’s hearing at that point, and that her best option was a cochlear implant.  He additionally concluded that further exposure from noise in the work environment would definitely decrease her hearing.

The employee was seen on November 8, 2012, by Dr. Phillip Rapport, an ENT/otolaryngologist, at the request of the self-insured employer.  In a report dated November 19, 2012, the doctor noted a history of deafness since childhood and that a younger brother also had a childhood hearing loss.  The employee stated that from June to November she frequently worked a 12-hour day in the imaging department.  She acknowledged she did not wear ear protection until 2012.  Dr. Rapport observed that the levels of measured noise were considerable and consistent with the employee’s description of a noisy environment.  The doctor noted, however, that the employee’s audiograms showed a hearing loss that was more progressive than what would be expected from noise exposure, and that none of the audiograms showed an “acoustic notch” at 4000 Hz which is typical of noise-induced hearing loss.  He further noted the employee’s hearing loss progressed at all frequencies, a finding more compatible with a familial etiology than noise exposure.  Dr. Rapport, accordingly, opined the employee’s work environment was not a substantial contributing cause of her current hearing loss.  In his opinion, it was more likely that her pre-existing familial hearing loss was the primary cause of her current hearing status.

By letter report dated April 25, 2013, Dr. Hilton noted the employee had a hearing loss since she was a young child, and reported gradual hearing loss in her right ear over the course of her life.  Dr. Hilton believed the primary etiology of the employee’s hearing loss was congenital.  Nevertheless, the doctor concluded her work audiograms did demonstrate a significant decline in her hearing thresholds between 2004 and 2012.  Dr. Hilton noted the employee worked 12-hour days, beyond the 8 hours recommended by OSHA for an 85 decibel work environment.  More importantly, according to Dr. Hilton, with her hearing aid in place, the programmed gain for the aid would deliver noise levels above those measured in the Pinnacle Engineering study.  Given his understanding of the hours the employee worked and the fact that for many years she wore a hearing aid amplifying the sound energy delivered to her right ear, it was his opinion that the noise levels in her work environment constituted a substantial contributing factor in her progressive hearing loss since 2004.

Dr. Rapport responded to Dr. Hilton’s report in a supplemental report dated August 23, 2013.  The doctor agreed that the energy level and duration of the noise to which the employee was exposed most likely did have a damaging effect on the inner ear since cumulative noise exposure eventually produces some degeneration of the inner ear.  However, Dr. Rapport maintained that he had not seen hearing loss in the low frequencies in cases of noise exposure.  He believed that because the employee’s hearing loss increased at all frequencies, her hearing loss was due to progression of her congenital condition as opposed to noise exposure.  Consequently, while Dr. Rapport agreed that noise exposure and especially the near OSHA threshold level noise exposure to which the employee was exposed would have an effect on the inner ear, it remained his opinion that the primary cause of her hearing loss was her congenital condition and that the noise exposure at work was not a substantial contributing factor to the employee’s hearing loss.

On September 10, 2013, Dr. Hilton responded to Dr. Rapport’s report.  While he agreed that noise exposure hearing loss typically affects high frequency hearing, and that the employee’s pattern of progressive hearing loss was not typical for a noise exposure injury, he believed it was problematic to apply patterns of hearing loss identified in otherwise healthy ears to someone with a congenital hearing loss.  Dr. Hilton stated that given the documented noise exposure, the documented decline in hearing thresholds over the same time period, and the known vulnerability to injury of the employee’s inner ear, it remained his opinion that the employee’s work environment did constitute a substantial contributing factor in the deterioration of her hearing.

By letter report dated January 23, 2014, Dr. Froymovich noted that in the past, the employee had been able to function quite well in her environment with a hearing aid, but had recently been working in an environment of loud ambient noise exceeding 80 decibels on a continuous basis.  Dr. Froymovich stated that someone who already has significant hearing loss who is exposed to continuous sound over 80 decibels is more likely to sustain further irreversible damage, and in his opinion the employee’s profound hearing loss in the right ear was facilitated by continued noise exposure and lack of ear protection at work.

Finally, Dr. Rapport received and reviewed some of the employee’s voluminous medical records dating back to her early childhood.  In his opinion the early audiograms were particularly important additions.  In a supplementary report dated April 4, 2014, Dr. Rapport noted the audiograms show poor hearing at a very young age and progressive decline through 1993 when she was a teenager.  Dr. Rapport believed the fact that the employee’s hearing loss got worse between 1983 and 1993 was indicative of an ongoing degenerative process that most likely continued into adulthood.  It was his opinion that this progressive degenerative process was the most likely cause of the continued worsening noted on the audiograms from 2004 through 2012.  Dr. Rapport maintained the employee’s progressive loss of hearing in the low frequencies was indicative of an intrinsic process as opposed to damage from environmental noise.  He further reviewed the employee’s work hours records, noting there was variation in the hours worked.  Dr. Rapport did not believe that the hours the employee worked or her degree of noise exposure were as important a consideration as the fact that she had an underlying congenital condition which was the main cause of her hearing loss.

On August 8, 2012, the employee filed a claim petition seeking payment of medical expenses incurred for evaluation and treatment of her right ear hearing loss.  The self-insured employer denied liability asserting her hearing loss was the result of a pre-existing condition and was not causally related to her work activities.  Following a hearing on April 11, 2014, the compensation judge found the employee did not sustain an injury in the nature of an aggravation or acceleration of her right ear hearing loss as a result of her work activities at the employer.  The employee appeals.

On appeal, the Workers’ Compensation Court of Appeals must determine whether “the findings of fact and order [are] clearly erroneous and unsupported by substantial evidence in view of the entire record as submitted.”  Minn. Stat. § 176.421, subd. 1.  Substantial evidence supports the findings if, in the context of the entire record, “they are supported by evidence that a reasonable mind might accept as adequate.”  Hengemuhle v. Long Prairie Jaycees, 358 N.W.2d 54, 59, 37 W.C.D. 235, 239 (Minn. 1984).  Where evidence conflicts or more than one inference may reasonably be drawn from the evidence, the findings are to be affirmed.  Id. at 60, 27 W.C.D. at 240.  Similarly, findings of fact should not be disturbed, even though the reviewing court might disagree with them, “unless they are clearly erroneous in the sense that they are manifestly contrary to the weight of the evidence or not reasonably supported by the evidence as a whole.”  Northern States Power Co. v. Lyon Food Prods., Inc., 304 Minn. 196, 201, 229 N.W.2d 521, 524 (1975).

In determining the employee failed to prove she sustained an injury in the nature of an aggravation or acceleration of her right ear hearing loss as the result of noise exposure at the employer, the compensation judge accepted the opinions of the self-insured employer’s medical expert, Dr. Rapport.  The employee argues the compensation judge erred in rejecting the opinions of the employee’s treating physicians, Dr. Hilton and Dr. Froymovich, asserting their opinions are supported by adequate foundation.

The question of foundation goes to an expert’s qualification to render an opinion.  The competency of a witness to provide expert medical testimony depends upon both the degree of the witness’s scientific knowledge and the extent of the witness’s practical experience with the matter which is the subject of the offered testimony.  Drews v. Kohl’s, 55 W.C.D. 33, 37 (W.C.C.A. 1996) (citing Reinhardt v. Colton, 337 N.W.2d 88, 93 (Minn. 1983)).  In this case, there is no dispute as to the expert qualifications of all three doctors or their familiarity with the employee’s medical care and treatment related to her hearing loss.

The compensation judge instead found the opinions of Dr. Hilton and Dr. Froymovich less persuasive than those of Dr. Rapport.  The judge explained that neither Dr. Hilton nor Dr. Froymovich reviewed the employee’s audiometry tests for the years from 1983 through January 2004, before the employee started working for the employer.  In addition, the compensation judge concluded that Dr. Hilton and Dr. Froymovich based their opinions in part on the incorrect information that the employee had worked 12-hour days throughout the years she worked for the employer - - an assumption the judge concluded was inconsistent with the employee’s time records.

The employee asserts that audiometric testing for years prior to 2004 was not relevant or necessary to the opinions of her treating physicians as there is no dispute that the employee has a congenital, progressive hearing loss condition.  She contends the audiometric testing in the employer’s personnel file, along with the January 27, 2004, audiogram at Associated Hearing, sufficiently establishes an acceleration or aggravation of the employee’s right ear hearing loss during the time she was working for the employer.

The issue in this case, however, is not simply whether there has been progressive hearing loss in the employee’s right ear since 2004.  There clearly has been.  The question is whether the employee’s noise exposure in the workplace was a substantial contributing cause of the acceleration or aggravation of her hearing loss.  There was conflicting expert medical opinion on this point.  The ultimate determination of medical causation is within the province of the compensation judge.  Felton v. Anton Chevrolet, 513 N.W.2d 457, 50 W.C.D. 181 (Minn. 1994).  Where there is adequate foundation for the opinion adopted by the judge, this court must normally uphold the compensation judge’s choice among medical experts.  See Nord v. City of Cook, 360 N.W.2d 337, 342-43, 37 W.C.D. 364, 372-73 (Minn. 1985).  We cannot conclude the compensation judge erred in adopting the opinion of Dr. Rapport on the facts of this case.

The employee contends the reports of Dr. Rapport do not contain a clear opinion that the noise exposure at the employee’s workplace was not a causative factor in the employee’s progressive hearing loss.  Instead, the employee maintains, Dr. Rapport stated only that he did not believe the employee’s exposure to noise at work was as important a consideration as the fact that she had an underlying condition which was the main cause of her hearing loss.  Thus, the employee argues, while the doctor’s reports indicate that congenital/familial factors are more important or significant, they do not eliminate noise exposure as an appreciable factor contributing to the acceleration or aggravation of the employee’s right ear hearing loss.

The employee has the burden of proving that her work environment caused her disability.  It is not necessary, however, for the employee to show that the noise exposure was the sole cause of her disability.  It is only necessary to show that the injury was a legal cause, that is, an appreciable or substantial contributing cause.  Salmon v. Wheelabrator Frye, 409 N.W.2d 495, 40 W.C.D. 117 (Minn. 1987).

In this case, the compensation judge reviewed the employee’s medical records, including the pediatric records, starting in 1978, and audiograms from 1982 through 2012.  The judge discussed in detail the hearing loss documented in the audiograms, concluding the tests demonstrated ongoing, significant and progressive deterioration of the employee’s hearing at all frequencies over time.  In particular, the compensation judge concluded the audiometric testing in 1983, 1993, 2004, and 2012 showed essentially the same progression of hearing loss over the course of 30 years in the right ear.

The compensation judge stated it was Dr. Rapport’s opinion that the employee’s hearing loss was primarily due to an intrinsic degeneration of her right ear, and was not substantially contributed to by her work at the employer.  The judge found persuasive Dr. Rapport’s explanation that in his experience of reviewing many cases of noise-induced hearing loss, he had not seen noise exposure cause hearing loss in the low frequencies, and that the employee’s hearing loss increased across all frequencies.  She accepted Dr. Rapport’s opinion that the employee’s hearing loss was a progressive, degenerative process related to recurrent ear infections and some type of familial process, and concluded that a preponderance of the evidence did not establish that the employee’s exposure to noise at the employer was a substantial contributing factor to the aggravation or acceleration of the employee’s right ear hearing loss.

Where evidence conflicts or more than one inference may reasonably be drawn from the evidence, the findings are to be affirmed.  Hengemuhle v. Long Prairie Jaycees, 358 N.W.2d 54, 60, 37 W.C.D. 235, 240 (Minn. 1984).  It is not the role of this court to re-evaluate the credibility and probative value of the evidence submitted and to choose different inferences than the compensation judge.  Whether this court might have viewed the evidence differently is not the point, but whether the findings of the compensation judge are supported by evidence that a reasonable mind might accept as adequate.  See Redgate v. Sroga’s Standard Serv., 421 N.W.2d 729, 734, 40 W.C.D. 948, 957 (Minn. 1988).  While there is language in Dr. Rapport’s reports that could be read as indicating that the employee’s exposure to significant noise levels at her workplace did have some role in her hearing loss, Dr. Rapport also specifically expressed the opinion that the employee’s exposure to noise was not a substantial contributing factor to her right ear hearing loss.  The medical records in combination with Dr. Rapport’s opinions adequately support the compensation judge’s determination.  We must, accordingly, affirm.