Etymotic's HD-15 High-Definition electronic earplugs let users hear normally when things are quiet, but kick in when sudden loud noises occur
If you work someplace where sudden loud noises frequently but intermittently occur, it can get kind of frustrating – you pretty much have to choose between protecting your hearing with ear plugs, or being able to hear what people are saying when it isn’t noisy. Your basic earplugs, unfortunately, don’t let you hear when things are quiet, but then activate when loud noises occur. Non-basic earplugs, however, do that very thing. Etymotic Research’s HD-15 High-Definition electronic earplugs contain tiny microphones, that instantaneously cause the plugs to block incoming sound waves when they detect noises over a given threshold. When the noise has ceased, the earplugs let the user hear normally again.