The ZEM Hearing Protection Device

Introduced in 2004 by SensGard, ZEM hearing protection is fundamentally different from traditional ear plugs and ear muff hearing protectors.

SensGard ZEM hearing protector

At first glance, ZEM hearing protectors look like a pair of small snorkels worn on the ears. They hardly look like they would be very effective hearing protectors, since there's nothing to seal the sound out of the ear. That's because they don't work by blocking sound out, like ear plugs and muff protectors do, nor do they use any electronics. Instead, they use a patented sound chamber technology. And independent testing shows that they are every bit as effective as the more familiar traditional hearing protection methods.*

How do they work? According to SensGard's company literature, the "snorkel" tube is actually a closed sound chamber that acts as an extension of the ear canal. Since it is larger in diameter than the ear canal, it offers less resistance to the sound waves and draws them inside, directing them away from the ear canal. Once inside, the ZEM uses the mechanical properties of sound waves to refract and cancel them.

"ZEM" stands for "Zwislocki Ear Muffler," named after the university professor who developed and patented the technology. SensGard began marketing ZEMs in 2004. In the UK, the product is sold under the Napier brand as the Napier Pro 9 and Pro 10.

One notable feature of the ZEM is that it lets you hear speech better than with some other forms of hearing protection that rely on acoustic blocking. The reason is that it is the lower frequency sounds that mask speech, and the ZEM provides a consistent level of noise reduction across low- and mid- range frequencies. At the same time, it provides a greater level of protection from higher frequencies — the ones most likely to damage your hearing.†

The ZEM offers a number of other advantages, especially compared with ear muff hearing protectors:
  • It is compact and lightweight, making it comfortable to wear even in hot, humid weather.
  • It can be worn with glasses, with no reduction in effectiveness.
  • For long gun shooters, it does not interfere with the gunstock, as muff protectors often do.

Compared with ear plugs:
  • It is non-intrusive and hygienic.
  • It is quick to put on and take off.
  • It is easy to use properly, to consistently get the maximum protection.

One disadvantage is that you can't use it together with ear plugs or ear muffs to get double protection.

The ZEM comes in two versions, depending on whether you want a medium level noise reduction rating (NRR 26) or a higher level (NRR 31).

* Kevin Adam, "Napier Pro9," in "'s Mammoth Hearing Protection Test 2009,", 18–19.
National Institute for Occupational Safety and Health (NIOSH), Product Detail for SensGard ZEM SGHP1-26, in "Hearing Protector Device Compendium" (2003).

SensGard ZEM hearing protector

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