Study Design and Participants
The present study involved the pretest data collected as a part of an ongoing hearing protection and cardiovascular disease prevention intervention study. Firefighters were recruited to participate in the study from occupational health clinics, fire departments, or a hearing test clinic in three states (California, Illinois, and Indiana) in the United States. A total of 722 firefighters from over 35 fire departments were recruited between March 2010 and May 2011. Among them, a total of 404 had actually participated in the study, resulting in response rate of 56% (404/722). All study protocols were approved by the Committee of Human Research of the University of California San Francisco and the Institutional Review Board of NorthShore University Health Systems in Glenview, Illinois, inthe UnitedStates. Informed consent was obtained from all interested volunteers before completingthepretestsurvey,audiometrictests,andinterventions.Audiometrictestswereadministeredbycertifiedstaffin the occupational health clinic, audiologist’s office, or fire departments. Participants completed the survey and training online in the clinics or fire departments right after the audiometric tests or at their own convenience in their preferred location where internet access was available.