Silencer Saturday #423: Silencers And Overpressure Risk, Part II

Good afternoon, everyone, and welcome back to TFB’s Silencer Saturday, brought to you by Yankee Hill Machine, manufacturers of the new Victra 20-gauge shotgun suppressor. Last week, we looked at blast overpressure risk from shooting small arms, particularly indoors. This week, we are turning to testing that maps these risks with suppressed firearms.

Silencer Saturday @ TFB:

• Silencer Saturday #422: Can Silencers Protect From Overpressure Risk?
• Silencer Saturday #421: Should You Change Your NFA Ownership Structure
• Silencer Saturday #420: Peculiar Patents
• Silencer Saturday #419: Reflex Resurgence
• Silencer Saturday #418: Lawsuit And Legislation Update

Hearing Safe?

There was a period of many years where manufacturers were applying the label “hearing safe” to their suppressors with reckless abandon. The common defense of that label came from an OSHA document which stated, “Exposure to impulsive or impact noise should not exceed 140 dB peak sound pressure level.” Manufacturers took that to mean, “if our silencer measures 139.9 dB that means it is safe” which is not an accurate summary of the OSHA guidance. Stating the 140 dB is a sound level not to be exceeded is very different than saying unlimited exposure to sound levels below that is safe.

I fell victim to that marketing when I was first getting into silencers. I thought that a silencer tested at less than 140 dB meant that hearing protection was not necessary. That was wrong, and I have the hearing damage to prove it. There are many complicating factors that a simple numerical dB value cannot capture. One time, I was up on a ridge shooting down into a valley. It was very steep, and there were limited options for setting up, with the best firing position being between two large boulders. I fired a 6.5 Creedmoor with the original SilencerCo Harvester in that space, and the sound felt like being struck in the head. The Anchor Brake redirected that sound into the rock walls beside me, and it was deafening.

Eventually, I wised up and started wearing hearing protection while shooting many of my suppressed setups. There are a few that truly do not need secondary hearing protection, like a .22 LR rifle with a suppressor, but those are few and far between. Ear protection is still a good idea even with a silencer!

PEW Testing

Pew Science is a name that will be familiar to most of our readers. Testing silencer performance has always been a tricky proposition. Test equipment is expensive and must be configured properly, and even when it is, comparisons of only the peak decibel level recorded do not tell the full story. Other elements of the sound, like pitch, can change how suppressors sound even if the absolute decibel value is the same.

The Silencer Sound Standard is a testing approach that provides a more complete picture of how effective various suppressors are at controlling hearing impact. Rather than simply using the peak dB, it factors in other aspects like the duration of the pressure. The resulting scores are not provided in units but on a comparative scale, with 1 being really loud and dangerous to your hearing, and 100 being very safe to be around for extended shooting.

This testing has been invaluable in helping shooters pick the right kind of suppressor for their use. If you are using a hunting rifle for one or two shots per season (hopefully), the exposure risk is very different than thousands of rounds per year on a short-barrel 5.56 inside a shoot house. Matching the protection level to the exposure risk helps shooters tailor their purchases to what they actually need.

PEW Hazard Maps

Their newest testing methodology is the PEW SOFT-HD Silencer Hazard Map. Much like the Silencer Sound Standard, the Hazard Maps depict levels of risk. With a top-down view of the shooter, the map shows higher-risk areas in red, shifting to lower-risk areas in green. This shows both the exposure for the shooter and any bystanders.

Much like a topographical map, “elevation lines” show the areas of higher and lower sound intensity. Those lines mark sound ratings based on the Silencer Sound Standard, with lines every ten points on the scale. The lines then bound the areas of relative sound levels.

These maps exist for both bolt-action and semi-automatic firearms. The most obvious way to distinguish the two (other than the labels on the images…) is the area of sounds pressure around the ejection port on the semi-autos. Bolt actions have an advantage there, and is shows up on the map.

Another interesting capability of the maps is performance of suppressors near walls, not just in open fields. The maps show the reflection of sound back from those surfaces. Much like my story above with shooting the silencer with a secondary brake in a confined space, those reflections can differ widely between silencers. The maps can help users understand what risks they are exposed to both indoors and outdoors. Circling back to the overpressure discussion from last week, sound is just pressure, and areas with less pressure will have less risk for the user.

These advancements in scientific testing show visually what many of us have noted through use. But instead of an anecdote that cannot be quantified, they show comprehensible data. It is an exciting time to be involved in the silencer world, and these kinds of developments will surely push silencer design and performance forward as manufacturers start incorporating this testing in product development.

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