In the Swiss army instructors and fortifications guards are exposed to firearms' noise which harms the ear. It was investigated whether the decline in the cases of acute acoustic traumas in non-professional soldiers serving in the army from 1987 to 1996 also was detectable in army instructors and fortifications guards (professional soldiers) and whether these persons were wearing hearing aids (as an indicator of hearing loss) more often than the average of the male Swiss population. First, we analyzed a historical time series of the incidence density of acute acoustic traumas in non-professional soldiers as well as in army instructors and fortifications guards. Second, we compared the prevalence rate of wearing a hearing aid in army instructors and fortifications guards with the male Swiss population. The incidence density for acute acoustic traumas in army instructors and fortifications guards observed over ten years showed no significant change whereas among non-professional soldiers a strong decline (-12% per year) was observed. The prevalence rate of wearing a hearing aid in army instructors and fortifications guards was significantly higher (RR 3.91 [95% CI 3.09-4.96]) than in the male Swiss population. These results suggest increased hearing impairment among army instructors and fortifications guards which is probably due to the high exposure to impulse noise events (occupational disease). It is recommended that these persons be subjected to a compulsory prevention program.