Interesting! When I was serving in the Canadian Navy back in the late '50s, we were given gunnery training using a 4" deck gun on a Frigate and balloons for target practice. Our protection consisted of wads of toilet tissue stuffed into our ears. I have since discovered that my present profound hearing loss is a direct result of this training (plus my years playing guitar in a band). I sure wish we had something better to protect our hearing back in the day - anything!
My hearing is severe due to no hearing protection back in the late 1960s and 1970s. At least there was never any protection to be seen available in the needed areas. I just came from the VA clinic and the Audiology department waiting area was full