- Significant contribution (of employment to ongoing condition)
- Initial entitlement (eligibility)
- Hearing loss (sensorineural)
The issue under appeal was whether the worker had initial entitlement to benefits for NIHL, as a result of noise exposure while working in the course of his employment.The appeal was allowed.OPM Document No. 16-01-04, "Noise- Induced Hearing Loss, On/After January 2, 1990" provides three factual criteria of "persuasive evidence of work-relatedness" in NIHL claims: i) continuous exposure to the equivalent of 90 dBA pf noise for 8 hours per day, for a minimum of five years; ii) a minimum bilateral hearing loss after taking into account age-related hearing loss (referred to as presbycusis); and, iii) a "pattern of hearing loss consistent with noise-induced sensorineural hearing loss" referred to as the "4000 Hz audiometric dip" or "notch". The first two criteria were met in the worker's case. On an audiogram chart, the "4000 Hz notch" appears as a marked drop in air conduction and bone conduction hearing values of sound at that frequency. In the case of the worker's audiograms, all three charts had a "cookie bite" shape. The term "cookie bite" shape means that the hearing loss deteriorates from 250 Hz and 500 Hz to a low around 1000 Hz and 2000 Hz, and improves slightly at 4000 Hz and again at 8000 Hz. This presents as a shallow U chart line or a "bite" from a cookie. This differs from the "4000 Hz notch" in that the latter is represented by a slight loss at lower and mid-range frequencies with a marked drop off at the 4000 Hz frequency, and improvement in hearing sensitivity at the 8000 Hz.Drawing upon Decision No. 105/21, the Vice-Chair noted that although the "cookie bite" pattern may be indicative of a hereditary or congenital cause of hearing loss, this etiological interpretation is not necessarily exclusive of other causes. The Vice-Chair found that the evidence, considered on a balance of probabilities, supported a finding that the worker's occupational exposure to noise made a significant contribution to his hearing loss, while recognizing that a component of the worker's hearing loss was caused by non-occupational causes.