| Summary: | Forest logging is the process in which trees are cut down for forest management and/or
timber harvest. According to OSHA, logging is the most dangerous occupation in the United
States. It consistently represents one of the most hazardous industries, with a fatality rate more
than 21 times higher than the rate for all workers in the United States. Yet, little research has
been performed to determine the long term effect of noise on forest loggers. OSHA regulations
state that the maximum permissible hearing in an 8 hour shift should not exceed 90 dB.
Occupational noise exposure is recognized as a primary factor on permanent hearing loss
(OSHA, 2007). The objective of this study is to determine whether long term hearing loss in
forest loggers is associated with noise emitted by logging equipment.
This study compares the differences in hearing thresholds of the participants, applying
the OSHA age correction tables for audiograms (OSHA, 2008). These tables present the hearing
threshold of a normal population at ages ranging from 20 to 60 years. Hearing threshold shift is
determined by subtracting the hearing threshold of each participant from age corrected hearing
threshold as defined by OSHA (2008) for each specific age. These individuals had never
experienced any type of acute or chronic hearing loss. Participants were also separated into age
groups of 10 year intervals (20 to 29, 30 to 39, 40 to 49, and 50 to 59) and experience groups of
10 year intervals (1 to 10, 11 to 20, 21 to 30, and 31 to 40).
The hearing tests on forest loggers determined that at 4000 Hz, the mean hearing
threshold of the participants was significantly higher than the rest of the frequencies.
Furthermore, a significant increase in hearing threshold between the participant population and
the hearing threshold of a normal population was also determined. The hearing threshold shifts at
1000, 2000, and 4000 Hz were of 4.9, 9.5 and 18.0 dB respectively. A significant decrease in the
hearing threshold (of 3.4 dB) was found between those participants who wore hearing protection
and those who did not.
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