Electronic Level-Dependent Hearing Protectors
These HPDs use electronic technology to maintain, and in some cases enhance, hearing ability when sound levels are low. They are often referred to as “active” hearing protectors. Environmental microphones (also referred to as tactical, surround, or situational-awareness microphones) on the device pick up the low-level (non-hazardous) sounds in the area around the wearer and reproduce them inside the hearing protector. Typically the wearer can control the loudness using a volume control on the device. The amount of sound that is electronically reproduced inside the HPD decreases proportionally as the sound level outside the device increases.
Electronic compression is used to limit the level of the reproduced sound inside the headset to non-hazardous levels.
Since the maximum attenuation provided (in the absence of electronic reproduction) is based on the physical properties of the earmuff cups or earplugs that create the acoustic seal around the ear or in the ear, these devices provide protection against both impulse and continuous noises in the same way as traditional HPDs. The big difference is the ability of electronic level-dependent HPDs to allow the wearer to hear more effectively during periods of low noise without the need to remove the device.
All 3MTM PELTORTM electronic level-dependent hearing protectors limit the sound
reproduced from the environmental microphones to 82 dB SPL. In the absence of the reproduced signal [even if the active circuitry is powered off], some
sound will continue to be transmitted into the ear since the barrier created by the earmuff cups or earplugs themselves has the same limitations as does a traditional HPD. In other words, even electronic level-dependent hearing protectors eventually depend on the non- electronic components to help protect the wearer’s hearing.