Silencer Shop released their sound meter test data for of the Griffin Armament Optimus sound suppressor.   We appreciate their work in putting it into some configs to give people a little insight into how it works in some of the applications and configs possible.

It was really a nice performing can across calibers.   During development we were impressed by that.

We use a B&K2209 like you.  The meter is old but it works really well and it is probably still the best meter to use for suppressor R&D.  There are only 2 meters that are mil-std compliant as far as I know the B&K2209 being one- both being decades old.  A lot of the companies are using systems that are not mil-std compliant, there is a Larson Davis meter for example we've been tempted to buy simply because it looks more modern- Sig is using one of those for example.  It is a 30 microsecond peak rise detecting meter, so it is a little slower than the ancient looking 2209.  Funny how you either look like you use ancient equipment or you get slightly less accurate data- you have to trade one problem for one solution because firearms suppressors are not a significant market segment for sound testing equipment sales, and sound level meters are not built for our industry but rather are sourced from the industrial safety marketplace for use in our industry.  

The really important criteria for an R&D meter is that it be portable and rapidly set up on site.  The Larson Davis meter (the old Mil-std and the new non mil-std models) do that, as does the B&K2209.  

The Pulse system is capable of mil-std metering as far as I know, but sound testing people complain about what a terrible pain in the ass it is to set up- talking about dragging a car battery around and essentially setting up an indoor lab outside.

All the more reason I'm buying one after 41f goes into affect

I haven't tested to see what the effect of using mil-std vs the Silencer Co / ASA proposed method is.

Mil-std is how we have tested and how we do R&D and testing- that samples 1M left of the muzzle of the unsuppressed barrel, and 1M left of the muzzle of the suppressor.  Silencer Co working with the ASA introduced the muzzle of the rifle both suppressed and unsuppressed method and Silencer Shop adopted it on their request as far as I know.  So all Silencer Shop testing as far as I know is done that way and has been since the Omega was tested in ~february 2015.   For example the second to last 762 can tested- the Rugged Razor hovered around 144DB in Silencer Shop testing, that is using the same testing Silencer Co / ASA standard they used here to test the Optimus. What my point is- is that there are several datapoints for comparison using the new testing method Silencer Shop is using- so when you mention that method, it wasn't integrated for the Optimus and we had nothing to do with that being used.

Whenever people talk about standards there are as many opinions as minds weighing on the subject, and we use Mil-std simply because it is what Gemtech, AAC, Surefire, KAC, and other industry companies use and have used for decades, but I feel what is most important is that performance comparisons are conducted using the same testing standard.  So silencer shop data compared to other silencer shop data is as scientific as anything else as far as we are concerned.   By the same token our testing for product performance ratings should be very comparable to Gemtech or AAC testing, as long as that was done to mil-std which most of it is.  When I say most the major exception is disclaimed testing using the shooters ear location which most companies do on occasion- an example being .338LM or 50BMG testing- applications where the major concern is that the shooters ear location be ear safe.

The comparison test of the Mil-STD to ASA methods was interesting.  Thanks for the post Tuuka.

The argument that some manufacturers use is that the muzzle of the gun doesn't change when you add a silencer. Therefore the location of the meter doesn't change. Not saying it's right or wrong but if everything is tested at the same location then you can compare apples to apples.

Silencer Shop explained their process/logic on their blog last year...here's the link.

I agree with you. However if some manufacturers are testing at the end of the silencer and others are not then it is not a fair comparison. So we chose to test everyone at the same location so that you can tell how they compare to each other.

No what I am saying is that if there is a universal test that is done the same way each time then you can accurately compare the dB ratings of each silencer. So by us testing at the muzzle then you can compare silencers tested by this method.

We will be doing a test soon to show what the difference is between testing at the muzzle vs testing at the end of the silencer. Mostly to show what the difference would be in dB ratings.

Philosophically if Silencer Shop uses Mil-Std then customers could unfavorably compare a product to a Silencer Co product which that product performance matches.    Obviously with two standards there are pro's and cons to using either so to some people either method will be wrong.  Really it would be more simple if companies in the industry didn't try to re-invent the wheel.  But they did.

I think it is probably important to understand the way mil-std ~10-20microsecond rise time, compares to ~30microsecond rise metering (something we might take a look at in the future by conducting some testing to help people understand the likely influence of differential rise time between these two types of systems).  

However; I don't think dropping to minimum theoretical rise time would do anything more than add another standard, further increasing the in-comparability of results on the market which would then vary by a factor of 9 from ~3-~30micro seconds where currently the comparability is only influenced by a factor of 2 from ~15-~30.  I believe the fastest available systems (which are not portable) have ~3-4 microsecond peak system rise time limitations and all that faster equipment is not really portable or affordable for industry companies, so that data is important to consider.  

So in my opinion as someone who has followed sound testing from the late 90's to present time, portable meters with mil-std, or with ~30microsecond peak rise time should be used for suppressor testing.  This limits testing to 2 older meters, and as far as I know 2 modern portable meters- both from Larson Davis and Bruel & Kjaer respectively.  Whenever testing is conducted, the meter used should be specified, so that people know which peak rise time approximately they are looking at.  

Hearing risk is rated based on time and SPL, so metering the absolute crests of peaks at nearly zero duration in time is probably not going to yield an accurate assessment of overall hearing risk.  I see the obvious reasons to meter very near to peak amplitude, but at the same time I also see reasons not to meter unrealistically short representations of peak sound for the purpose of a hearing damage risk assessment- that one number value used to represent a waveform of varying amplitude and duration.  For example, if we meter [completely hypothetically] 4DB louder at 1/3 or 1/4 the time of mil-std, does that mean that the SPL occurring in 1/4 of the already very short duration in time is more significant? I would say no.  Mil-std to ~30microsecond peak rise would be ~ twice the duration of sound- a little less substantial to the effect that my engineering hypothesis would be that ~20microseconds (where the military scientists wanted to be) is probably ideal for conducting this type of testing.  B&K 2209's sample at ~16microseconds and that is very near to that. My experience with cans metered on the 2209 is that cans ear metering at 140 do seem to be borderline dangerous to my ears (an unscientific perception), so I feel the mil-std A weighted results fairly closely parallel the OSHA risk limit for practical purposes.  This is supported by the fact that C weighted firearms impulse noise (what the OSHA scale is based on) is fairly close to A weighting of the same, and also by the fact that OSHA impulse noise is considered to be duration of less than 50 microseconds- in other words it was probably built around ~30microsecond equipment (what is more commonly available) running C weighting, so Mil-std A weighted at ~16microseconds is actually probably less lenient than the OSHA std for impulse noise.  The people arguing for faster sampling or different weighting are disregarding the fact that a new hearing risk scale would be required to interpret data taken with faster equipment.  That doesn't exist of course, so they are in essence arguing for a move to data that has no ability to be interpreted- like a new measuring system combining inch and metric that no one is familiar with.    Confusion would be the result of such a move.

Anything you find on this topic will be an opinion piece, because even the scientists are talking about analytical data, and then interpreting the results which is where their opinion comes into the argument.  What is not opinion but rather fact, is that over 2 decades of data at a ~20 microsecond standard exists, and that very recently, some industry motion to ~30 microsecond systems has occurred.

I looked at the manual for the B&K 2270 and that suggested the sampling rate of the B&K 2270 used by Silencer Shop is 20.1 microseconds [48KHZ], but the impulse peak is based on a 35 microsecond constant.  I couldn't find the data for sampling speed of the 2209 in A weighting but it appears to be equal or faster because the minor discrepancies in data trend toward the 2209 hearing a noise as louder - as far as I know only having sent products to be tested.  We haven't tested products on the same day in the same location with both meters so I can't be any more accurate than that.

Again rather than ask for unrealistic specs that most industry grade equipment is not capable of, the 20-30 microsecond arena I would consider ideal.  If anything needs to be done, it would be to revisit OSHA's risk level and develop risk limit parameters built for ~25 microseconds rather than 50 where it is.   This might for example move the 140DB limit to 143, which would probably soften the arguments that people have made that A weighting and mil-std are inadequate because the shorter duration of measurement would have to raise the risk limit because the 50 microsecond data used to develop the 140DB C weighted limit was probably substantially clipped.

Probably few if any.  We are selling them.  I've used it.  It works and adds functionality to the Optimus for end users who have A2 mounts or who own our A2 length or flash comp mounts and want to run a can some of the time.

I believe the recording they are talking about collection of the metered numbers which could occur by various means.  They are also allowing photographs of the screen of an attached oscilloscope. You can set up a 2209 to do that but most people read the dial and write the numbers down.  Historically multiple companies working directly with the government on suppressor programs used Larson Davis 800B's and B&K 2209's for 1474-D testing.  Very probably these companies realized that the testing was ultimately conducted by the military for selection, so it never really mattered whether they photographed a number or wrote it down.



That person would appear to be recording on paper, but maybe that person would be taking pictures of an oscilloscope as mentioned here:



I'm more concerned with consumer reports style testing for consumers than with the minutia of military standards.   I can't comment on what NATO or the military needs for sound testing (which is a shifting concept across time), but I can say that the suppressor industry has used 1474-D for ~20 years and that it provides single numbers that are useful to the consumer in helping to understand individual silencer performance.  

I would like to compare the B&K 2209 to the 2270 and Larson davis 831 to see how the numbers compared, and what the influence of ~30 microsecond rise time was, but that is as far as my interest goes.  I don't want to change the standard that I've seen as easily used and understood by consumers researching products for ~20 years.

As a company we realize engineers ultimately need efficient and reliable testing equipment, and often have to test off site, so portable equipment needs to be used for that.  In that respect I wouldn't fault a company for running a Larson Davis 831 if they couldn't find a 2209.  It doesn't help a company or an industry to force testing equipment on engineers that is so time consuming to set up that it reduces the frequency of testing in product development.   As time passes there will be less and less access to the old analog meters that are considered 1474-D compliant.  Unfortunately our industry demand for equipment is too small to drive equipment design.  So I believe the most applicable and available portable equipment should be used, and everything I've talked about is a reflection of that in today's market.

The 2209 is very accurate.  We can meter the same can twice with accuracy of a couple tenths of a DB (same day/platform/ammo)- and that shows consistency of the 10round testing method as well as the meter.  We can use the system to recognize performance gains in R&D as small as 1DB.   All the systems discussed are class 1.  

I'm not sure how bad the meter would have to be to see +-6DB but my guess is all the discussed systems would be more accurate than that.

Mil-std 1474-E has never been used as a silencer industry standard test.   They could have made the number 1500KHZ, it wouldn't have any validity in my discussion as a consumer market silencer company representative.  It is not uncommon for the government to ask for things that have no logical basis in reality.  That doesn't mean the private sector has to pay attention or pretend like they made intelligent decisions.  There is not one portable meter on the market capable of satisfying 1474-E.  If someone working a hired job wrote that specification, his boss would laugh him out of the office.

Nerds.

1474-D (your citation above) talks about data recording (AKA capture of information from the sound level meter), 1474-E is talking about the actual sound testing equipment sampling of information.  So 1474-D could be tested with a 2209 and a tape recorder or an oscilloscope like the military did do in August of 1968 during the Silencer Principles and Evaluations report and allowed for through 1474-D , but 1474-E appears to be made with the B&K Pulse system in mind.

The military also doesn't manufacture silencers, and people usually get a pat on the back for constantly moving goal posts that involve solicitations because the military has an unscientific belief that whatever specifications they request will ultimately be achieved by the industries supporting their purchases and that the end result will be positive.  Case in point the new modular handgun solicitation in which the military doesn't even want to rise to the level of responsibility required to ask for what it believes will be best- rather it asked for one gun that is multiple handguns in theory- a seat for every ass that I believe reduces the pistol to a soul less item like a screw-gun.  

Another point to keep in mind is that the only authority the military takes data from is itself.  So you don't have to test to 1474-E to sell a product to the military or to win a contract with it.  As an industry it will generally make more sense to test with portable equipment, or to at least have testing standards that support portable equipment.  For that reason 1474-D is a sensible standard for the industry to have and it makes sense to me why we use it.  

I just wanted to clarify because really you are talking about a nuance of the testing and the fact that all the industry companies and also all the independent testing authorities (Al Paulson, Robert Silvers, John Titsworth) have historically read the dial and not hooked up the oscilloscope and taken pictures of the screen.  

I understand your argument.  I'm glad I was able to get to the point I can say I see what you are driving at.  I don't feel it disqualifies the statement the industry as a collective whole has made for the last 20 years, that it tests to Mil-Std 1474-D.    I also don't see the data collection std which is unrelated to peak system rise time as a precedent to 1474-E for establishing that the peak system rise time was seen as not fast enough at 20 microseconds.