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Posted: 8/29/2026 8:39:29 PM EDT
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Hypothetically, if a person were to take advantage of the current situation regarding the NFA to build .22, .556, and .308 silencers, is there a relatively inexpensive way to accurately measure the sound levels in DB? My initial research indicates that phone apps and inexpensive meters are just totally ineffective for this, and that meters that actually work are very expensive. Is there some cost effective work around? |
The more the government tells us we should not do a thing or have a thing, the more crucial it is that we do those things and have those things.
<---- Used to do NVH work for automakers, I know a bit about noise measurement.  There are two major sources of variability in sound measurement - the environment is the biggest, the instrumentation is next. No one outside Automotive OEMs and movie/recording studios can afford a true hemi-anechoic chamber to get accurate repeatable measurements of any low frequency content. The best you can do is to control the measurement error so that it is consistent for A-B comparisons. I'll come back to measurement devices in a sec. The best work around for controlling environmental error is often referred to as a "sound shack". You are trying to measure something with a lot of low frequency content, which is hard, OTOH, maybe most of the sound you will suppress with the suppressor is in the higher frequency ranges. If someone can post a FFT of a gunshot, I can provide more detail, but my gut feel is that a typical reasonably sized sound shack will work well enough for repeatable measurements. There are a ton of methods to build them, but the easiest is probably just something like an open 2x10 frame, four walls and a ceiling. The walls, ceiling, and floor should NOT be parallel. You want heavy acoustically dead plywood or OSB glued (not nailed or screwed) to the outside. I suspect OSB is more dead than plywood, but I would have to look it up or ask Grok. On the inside, you want sound absorbent fiberglass batting or a similar product full depth of the 2x10's and another layer covering the insides such that the edges of the boards are not exposed. You can get AI to give you more detail on this, it is sort of similar to building a home theater room, but you want the walls to be vastly more absorbent. The size of the shack technically needs to be big, but the size required on paper is not practical due to the low frequency wavelengths, so again you're just trying to have a consistent error. I'm sure you could get AI to design this for you within the limitations of where you're testing. I do not think portability is possible, so this will be something you build at your range and shoot out of. My guess is a roughly 12'x15' footprint would do, but if you can go longer in the shooting direction (gun toward closed end, firing out through a smallish opening) that will be better. Again, consult AI. Obviously, you don't want variables like traffic or airliner overflights contributing to error, so you want to be remote. Now, WRT to measurement, you are correct that phones and the like will not be accurate. Their clipping and compression of high SPL and low frequency content is just too unpredictable to even produce a valid A-B comparison. The most cost-effective path for you would be rental of a higher end SPL meter. There are lots of places to do this. You want something more industrial-oriented because this will be loud and have so much low frequency content. Then you have to decide if you will use weighting (theoretically emulates human hearing) or not, and you must be ABSOLUTELY CONSISTENT in where the meter is relative to the gun muzzle and where both are inside the sound shack. Laser align them off a reference point. I probably would use a weighting scale, just be consistent in which one you use. A simple dB measurement though will only tell part of the story, and could be misleading at that. The best approach would be to collect data that you can perform an FFT on to get the frequency content of the shot. That will tell you in more detail what your suppressor design is doing or not doing. It is a much better way to measure design changes. If you want to go full retard, you can even rent a modal hammer and check the vibration modes of the suppressor. But then again, never go full retard.  This is probably more than you wanted. I could go on for a while, and Grok/Chat can go into even more detail. You can do things instantly with modern signal processing instantly that took me a day or more to run analyses on back in the day. In my prior lives, we used sound shacks to measure a lot of diverse sound sources, from little things like switchgear all the way up to offroad equipment, so it can be done. The key is not absolute perfection in the number, you will never, ever get there. The key is for your error to be consistent and repeatable. ETA, next best thing to a sound shack is a very large, relatively flat open field, preferably one with just heavy grass and no rock formations. You will also have to avoid windy days, and other environmental factors. There is actually a SAE standard for outdoor sites for measurement of sound content, can't recall the standard # though. The sound shack greatly minimizes environmental factors. Again you have to be dead accurate and repeatable in positioning of both measurement device and gun. |
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Originally Posted By flcracker: I have rented decibel meters for monitoring work spaces from environmental equipment rental companies in the past. About $50/day. Not for one that's rated for mil-spec firearm metering. First, there's only really 3 meters that would be applicable. 1 of those would likely be unobtainium. The other might have a chance of being rented, but, since there's very few of them and parts are scarce, the cost is most definitely not $50/day. The third, being the most up-to-date tech, is extremely costly to purchase so I would guess a weekly rental to be in the thousands of dollars. |
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Originally Posted By User55645: Not for one that's rated for mil-spec firearm metering. First, there's only really 3 meters that would be applicable. 1 of those would likely be unobtainium. The other might have a chance of being rented, but, since there's very few of them and parts are scarce, the cost is most definitely not $50/day. The third, being the most up-to-date tech, is extremely costly to purchase so I would guess a weekly rental to be in the thousands of dollars. Not needed for OP's purposes unless he expounds further. Mil-Spec uses massive sampling rates to determine the PRECISE moment that a bullet leaves the barrel, down to 0.00001 sec. That level of precision to compare suppressor performance, when all you really care about is human perception, is just not needed. |
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Originally Posted By VVinci: Not needed for OP's purposes unless he expounds further. Mil-Spec uses massive sampling rates to determine the PRECISE moment that a bullet leaves the barrel, down to 0.00001 sec. That level of precision to compare suppressor performance, when all you really care about is human perception, is just not needed. Originally Posted By VVinci: Not needed for OP's purposes unless he expounds further. Mil-Spec uses massive sampling rates to determine the PRECISE moment that a bullet leaves the barrel, down to 0.00001 sec. That level of precision to compare suppressor performance, when all you really care about is human perception, is just not needed. It's actually .000005sec, per MIL-STD-1474E, and the acoustic rise time starts slightly before the physical base of the bullet clears the muzzle crown  And I don't see how the OP asked for less than this accurately measure the sound levels in DB The closest thing outside the spec would most likely be a Larson Davis LxT-QPR, and even that could vary 3-10dB lower than actual and around 8dB louder on FRP. A possible 18dB swing, between shots, is no where near "accurate" when it comes to metering silencers. OP would be wasting his time and money with anything other than a 2209 or better. |
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Originally Posted By VVinci: Not needed for OP's purposes unless he expounds further. Mil-Spec uses massive sampling rates to determine the PRECISE moment that a bullet leaves the barrel, down to 0.00001 sec. That level of precision to compare suppressor performance, when all you really care about is human perception, is just not needed. Originally Posted By VVinci: Originally Posted By User55645: Not for one that's rated for mil-spec firearm metering. First, there's only really 3 meters that would be applicable. 1 of those would likely be unobtainium. The other might have a chance of being rented, but, since there's very few of them and parts are scarce, the cost is most definitely not $50/day. The third, being the most up-to-date tech, is extremely costly to purchase so I would guess a weekly rental to be in the thousands of dollars. Not needed for OP's purposes unless he expounds further. Mil-Spec uses massive sampling rates to determine the PRECISE moment that a bullet leaves the barrel, down to 0.00001 sec. That level of precision to compare suppressor performance, when all you really care about is human perception, is just not needed. @VVinci Tell that to Pew Science, lol. He uses a human ear dosing model / integral / weighting with very fast sampling to assess suppressor performance. You might find it interesting if you can wade through the verbosity and inflated ambiguous terms. https://pewscience.com/ |
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