Strategies to Hear for a Lifetime: 3. Protect Your Ears
Electronic
Hearing protectors can be built with microphones and speakers which are powered by a battery. The earplug or earmuff provides passive attenuation by sealing the ear, and the electronics provide a way to restore the ability to hear important sounds at a safe listening level.
For instance, hunters want to be able to hear the sounds in the environment yet be protected when they shoot the firearm.