Title page for ETD etd-03092000-18570023

Type of Document Master's Thesis
Author Christian, Erika
Author's Email Address Erika.Dabney@usa.xerox.com
URN etd-03092000-18570023
Title The Detection of Warning Signals While Wearing Active Noise Reduction and Passive Hearing Protection Devices
Degree Master of Science
Department Industrial and Systems Engineering
Advisory Committee
Advisor Name Title
Casali, John G. Committee Chair
Beaton, Robert J. Committee Member
Carter, Ned E. Committee Member
Robinson, Gary S. Committee Member
  • Active Noise Reduction
  • Active Noise Cancellation
  • Audition
  • Hearing Protectors
  • Hearing Protection Devices
Date of Defense 1999-07-15
Availability unrestricted
The research described herein was undertaken to determine how masked thresholds changed when individuals wore an active noise reduction (ANR) hearing protection device (HPD), a passive HPD, or no HPD. An ANR earmuff, a passive earmuff, and a user-molded foam earplug were tested in two types of noises (pink and red) at two different noise levels (85 dBA and 100 dBA). The signal used was an industry-standard backup alarm. The experimental design was completely within-subjects. An ascending method of limits was used to obtain 15-20 correct positive responses, which were then averaged to obtain the masked thresholds for each treatment condition. A visual probability monitoring task was incorporated in the experimental design to provide a loading task for the participants. In addition to masked thresholds, comfort and mental workload were assessed. Finally, participants were asked to rank each of the three HPDs with respect to their perceived ability to facilitate hearing the signal in noise.

Results indicated that in 85 dBA noise, masked thresholds were lower when hearing protection devices were worn, compared to the unoccluded condition. Additionally, the results indicated that the ANR device provided a significant advantage (lower masked thresholds) over the passive earmuff in the low-frequency biased red noise (across both noise levels) and the 100 dBA noise level (across both noise spectra). However, the ANR earmuff exhibited no significant advantage over the user-molded foam earplug in any of the conditions. Rather, the user-molded foam earplug produced significantly lower masked thresholds at 100 dBA. The results also indicated that there was no difference between the three devices in their perceived ability to facilitate detection of the signal. There was also not a significant difference in comfort ratings between the three HPDs, although there were several complaints about the comfort of the ANR earmuff during the experiment.

  Filename       Size       Approximate Download Time (Hours:Minutes:Seconds) 
 28.8 Modem   56K Modem   ISDN (64 Kb)   ISDN (128 Kb)   Higher-speed Access 
  etd.pdf 1.64 Mb 00:07:36 00:03:54 00:03:25 00:01:42 00:00:08

Browse All Available ETDs by ( Author | Department )

dla home
etds imagebase journals news ereserve special collections
virgnia tech home contact dla university libraries

If you have questions or technical problems, please Contact DLA.