5. INTERVENTIONS
5.1. Actual Interventions
5.1.1. Noise Irritation
Kalveram et al (1999) point out that much psychoacoustical
noise research has limitations because it is
based on the correlation between annoyance ratings
and physical measurements of sound energy, often
equivalent levels, leading to noise dose. To remove the
effects of this type of ergonomics risk, there were three
interventions. First, a clear, high density plastic (HDP)
cover was installed to contain the cutting tools to minimize
the irritation noise from the trim–form process
in CL. Second, earplugs with a noise-reduction rating
(NRR) of 30 dB were provided to workers in the CL
trim–form and testing processes, to ensure that every
worker in the trim–form processes used them. These
earplugs would reduce the noise from 115 dB to 85 dB.
Instruction of the correct earplug-wearing technique
(e.g., how to lift the ear, place the earplug in at the right
angle, and fit the plug comfortably into the ear) was
taught to all workers. Third, a special storage box with
spare earplugs was installed at the entrance to the work
process area for all workers and visitors.