Objective: This investigation was designed to determine the effectiveness of earmuffs worn by a single individual during shooting practice.
Design: Single subject experimental design.
Study sample: A 21-year old female recreational shooter, who practiced shooting on a regular basis while using earmuffs participated in the study. She reported occasional noise exposures of other types including car races and demolition derbies but no hearing difficulties or symptoms such as tinnitus. Her auditory sensitivity was within normal limits. On each test-day, distortion product otoacoustic emissions (DPOAEs) were recorded in a sound-attenuated booth before and after a shooting practice session conducted while using earmuffs. Data were collected across six different days, across six weeks, to allow recovery from each of the six shooting practice sessions. The participant was requested to refrain from other noisy activities in between sessions.
Results: Significant changes in DPOAE signal-to-noise ratios (SNRs) were apparent following the shooting sessions, at 1184 and 4761 Hz in the left ear suggesting that the hearing protection worn by the individual was insufficient to completely protect her hearing.
Conclusions: It is possible to assess the effectiveness of hearing protection worn by individual shooters using repeated measurements of DPOAEs embedded in a single case-research design.
Keywords: Hearing protection device; distortion produce otoacoustic emissions; earmuffs; hearing loss; noise; single case research.