Title page for ETD etd-02062013-040020

Type of Document Master's Thesis
Author Park, Min-Yong
URN etd-02062013-040020
Title Laboratory investigation of in-field influences on spectral noise attenuation and comfort of insert and circumaural hearing protectors
Degree Master of Science
Department Industrial Engineering and Operations Research
Advisory Committee
Advisor Name Title
Casali, John G. Committee Chair
Kemmerling, Paul T. Jr. Committee Member
Kroemer, Karl H. E. Committee Member
  • Noise control
Date of Defense 1989-08-28
Availability restricted

Laboratory-obtained, manufacturer—supplied hearing protector attenuation ratings typically overestimate the workers’ protection level In the workplace. ln addition, several work-related in-field factors often degrade protection performance ofthe hearing protection devices (HPDs), posing the threat of underprotection for industrial workers. This research investigated the effects of HPD wearing time, subject activity movement, and HPD fltting procedure on the frequency~specIflc attenuation and user-rated comfort achieved with a popular foam cushion earmuff, two types of earplugs (user-molded foam and pre-molded, triple-flanged polymer), and an earmuff over foam earplug combination. Both attenuation and comfort data were collected from 40 naive but audiometrically normal subjects. Using a psychophysical real-earattenuation- at—threshoId measurement procedure, attenuation data were obtained before, during, and after the activity movement tasks, which induced typical worker movements, so that the influence of wearing time and activity movement could be determined. Bipolar comfort rating data were also collected before and after the activity movement tasks, The results of statistical analyses indicated that achieved attenuation and user comfort signiflcantly decreased over a two-hour wearing period and that training to achieve better lltting markedly improved protection, although these changes were device- and frequency-specific. Loss in frequency-specific attenuation over the wearing period was up to 6.3 dB for all HPDs except the foam plug, and attenuation Improvement due to training ranged from 4 to 14 dB for all HPDs except the earmuff at 1000 Hz and below. Almost no difference In achieved attenuation or comfort was found between the two activity (head/torso and temporomandibular) movements, but the earmuff tended to slip during highly kinematic head/torso movement. In general, out of the four different HPD conligurations used in the study, the foam plug was very resilient to either type of activity movement but did benetit more than the other devices from the training for proper tilting; it was also perceived as the most acceptable and stable HPD by the subjects. ln summary, the research illuminated the strong influence of in-field factors on HPD effectiveness.

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