{"id":{"repo_id":"vt","oai_identifier":"oai:vtechworks.lib.vt.edu:10919/31434"},"canonical_url":"https://search.dev.ndltd.org/etd/vt/oai:vtechworks.lib.vt.edu:10919/31434","repository":{"repo_id":"vt","name":"Virginia Tech","base_url":"https://vtechworks.lib.vt.edu/oai/request"},"display":{"title":"The Detection of Warning Signals While Wearing Active Noise Reduction and Passive Hearing Protection Devices","abstract":"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.","abstract_html":"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.","abstract_has_math":false,"creators":["Christian, Erika"],"institution":"Virginia Tech","degree_name":"Master of Science","degree_level":"masters","degree_discipline":"Industrial and Systems Engineering","degree_department":"Industrial and Systems Engineering","school":null,"contributors":[],"advisors":[],"committee_chairs":["Casali, John G."],"committee_members":["Beaton, Robert J.","Carter, Ned E.","Robinson, Gary S."],"year":1999,"date_issued":"1999-07-15","date_published":"1999-07-15","updated_at":"2026-07-22T22:19:22Z","subjects":["Active Noise Reduction","Active Noise Cancellation","Audition","Hearing Protectors","Hearing Protection Devices"],"languages":[],"rights":["In Copyright"],"rights_urls":["http://rightsstatements.org/vocab/InC/1.0/"],"identifier_entries":[{"key":"dc:identifier.other","label":"Dc Identifier Other","values":["etd-03092000-18570023"],"render_values":[{"text":"etd-03092000-18570023","href":null,"code":true}]}]},"links":{"outbound_url":"http://hdl.handle.net/10919/31434","outbound_label":"Handle","outbound_source":"dc:identifier.uri"},"metadata_groups":[{"id":"people","label":"People","entries":[{"key":"dc:contributor.committeechair","label":"Committee Chair","values":["Casali, John G."]},{"key":"dc:contributor.committeemember","label":"Committee Member","values":["Beaton, Robert J.","Carter, Ned E.","Robinson, Gary S."]},{"key":"dc:contributor.department","label":"Department","values":["Industrial and Systems Engineering"]},{"key":"dc:creator","label":"Author","values":["Christian, Erika"]}]},{"id":"academic_context","label":"Academic Context","entries":[{"key":"dc:date.accessioned","label":"Dc Date Accessioned","values":["2014-03-14T20:32:27Z"]},{"key":"dc:date.available","label":"Dc Date Available","values":["2014-03-14T20:32:27Z","2001-05-19"]},{"key":"dc:date.issued","label":"Date","values":["1999-07-15"]},{"key":"dc:publisher","label":"Institution","values":["Virginia Tech"]},{"key":"dc:type","label":"Dc Type","values":["Thesis"]},{"key":"thesis:degree_discipline","label":"Discipline","values":["Industrial and Systems Engineering"]},{"key":"thesis:degree_level","label":"Degree Level","values":["masters"]},{"key":"thesis:degree_name","label":"Degree Name","values":["Master of Science"]},{"key":"thesis:institution_name","label":"Thesis Institution Name","values":["Virginia Polytechnic Institute and State University"]}]},{"id":"subjects_keywords","label":"Subjects and Keywords","entries":[{"key":"dc:subject","label":"Dc Subject","values":["Active Noise Reduction","Active Noise Cancellation","Audition","Hearing Protectors","Hearing Protection Devices"]}]},{"id":"language_rights","label":"Language and Rights","entries":[{"key":"dc:rights","label":"Dc Rights","values":["In Copyright"]},{"key":"dc:rights.uri","label":"Rights URI","values":["http://rightsstatements.org/vocab/InC/1.0/"]}]},{"id":"identifiers","label":"Identifiers","entries":[{"key":"dc:identifier.other","label":"Dc Identifier Other","values":["etd-03092000-18570023"]},{"key":"dc:identifier.uri","label":"Identifier URI","values":["http://hdl.handle.net/10919/31434"]}]},{"id":"additional","label":"Additional Metadata","entries":[{"key":"dc:description.abstract","label":"Abstract","values":["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."]},{"key":"dc:description.degree","label":"Dc Description Degree","values":["Master of Science"]},{"key":"dc:title","label":"Title","values":["The Detection of Warning Signals While Wearing Active Noise Reduction and Passive Hearing Protection Devices"]}]}],"canonical_facts":{"dc:contributor.committeechair":["Casali, John G."],"dc:contributor.committeemember":["Beaton, Robert J.","Carter, Ned E.","Robinson, Gary S."],"dc:contributor.department":["Industrial and Systems Engineering"],"dc:creator":["Christian, Erika"],"dc:date.accessioned":["2014-03-14T20:32:27Z"],"dc:date.available":["2014-03-14T20:32:27Z","2001-05-19"],"dc:date.issued":["1999-07-15"],"dc:description.abstract":["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."],"dc:description.degree":["Master of Science"],"dc:identifier.other":["etd-03092000-18570023"],"dc:identifier.uri":["http://hdl.handle.net/10919/31434"],"dc:publisher":["Virginia Tech"],"dc:rights":["In Copyright"],"dc:rights.uri":["http://rightsstatements.org/vocab/InC/1.0/"],"dc:subject":["Active Noise Reduction","Active Noise Cancellation","Audition","Hearing Protectors","Hearing Protection Devices"],"dc:title":["The Detection of Warning Signals While Wearing Active Noise Reduction and Passive Hearing Protection Devices"],"dc:type":["Thesis"],"thesis:degree_discipline":["Industrial and Systems Engineering"],"thesis:degree_level":["masters"],"thesis:degree_name":["Master of Science"],"thesis:institution_name":["Virginia Polytechnic Institute and State University"]},"updated_at":"2026-07-22T22:19:22Z"}