Instructional requirements for using the HML and NRR methods for estimating protected exposure levels under hearing protectors

• Main Author: Thomas, William C.
• Other Authors: Industrial and Systems Engineering
• Format: Others
• Language: en
• Published: Virginia Tech 2014
• Subjects: LD5655.V855 1995.T466
• Online Access: http://hdl.handle.net/10919/46415; http://scholar.lib.vt.edu/theses/available/etd-12232009-020645/

A study was conducted to investigate the effectiveness of different instructional tools for teaching individuals to calculate a protected hearing level given A- or C-weighted sound levels, and using the NRR and HML methods. Three instructional tools were evaluated: 1) outline instructions, 2) tabular nomogram, and 3) hypermedia computer-based instructions. Effectiveness was measured in terms of calculation time and proportion of errors made. The results yielded no statistically-significant differences between the tools. All subjects performed equally well using each tool for the NRR method, and equally poor using each tool for the HML method. Two additional topics of investigation included a baseline of knowledge determination for hearing conservationists, and an inquiry into the subjective discrimination of various sound spectra. The baseline of knowledge determination evaluated the ability of subjects to calculate a protected hearing level, given A- and/or C-weighted sound levels and the NRR. Since professionals in this field are responsible for determining OSHA compliance, this test should have resulted in high baseline scores. However, only 50% of the subjects could calculate a correct answer given the C-weighted sound level; only 17% could calculate a correct answer given the A-weighted level. The spectral discrimination portion of the study evaluated the ability of an individual to subjectively classify noises as high frequency-dominated, or low-frequency-dominated. Of the 12 pink and industrial noises used, only three could be correctly identified more than 90% of the time. This suggests that subjective classifications of noises should not be relied upon. === Master of Science