Earmuff effectiveness against chainsaw noise over a 12-month period.
A study measuring the ability of new Peltor H7P3 Grade 4 helmet-mounted earmuffs to reduce the level of chainsaw noise reaching forestry workers' ears was undertaken over a one-year period. The objective was to establish effective replacement guidelines for earmuffs. The results showed that the earmuffs provided effective hearing protection for the subjects over the one-year test period. There were no statistically significant changes in field attenuation levels during the first 9 months. While the following three-month period (9-12 months) did experience a significant 3 dB(A) decrease, mean inside microphone noise level measured at the 12-month stage was 78.8 +/- 3.0 dB(A). This level is well under the damage risk criterion of Leq (8 hour) not exceeding 85 dB(A). It was noted during the study that a large proportion of the earmuffs would normally have been replaced before the 12-month stage owing to the discomfort associated with cushion deterioration. Results suggest that Peltor H7P3 grade 4 helmet-mounted earmuffs could be safely used as an effective form of chainsaw noise protection in a production forestry environment for a maximum period of 12 months before cushion replacement.
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New Zealand Logging Industry Research Organization, PO Box 147, Rotorua, New Zealand.