With a slow rise time and low sample rate I've seen scattered results. You guys calling telling me the Ultra 9 is 5dB louder than a 30P-1 shows what happens with a slow rise and and low sample rate combined. Like I said look at my link and start at slide 32. It explains it pretty well

We have had to do some down range testing to show the military that what they are asking for isn't doable due to the sonic crack.

Late to the game - adding in our .02

1. William - cool vid appreciate the review, the SR-5 is a hell of a can.
2. Don't get caught up on numbers, too many inconsistencies and variables.
3. A good meter will run $50K plus the lab to control the testing.
4. Science matters - We have a anechoic chamber in the lab for our custom B&K Pulse system
5. Numbers don't mean sh*t on paper

One last thing before this thread really derails... We post actual repeatable readings we record during testing of the product and post host and ammo used. Our numbers are as accurate and as truthful as humanly possible.

That slide was from tests that I did with the California state crime lab around 9 years ago. I use a Larson Davis 800B with their 1/4" mic (#2530, which is a clone of the B&K 4136). LD claims that the rise time of the LxT1-QPR is 30 microseconds or better, and one of the LD engineers told me that the best a digital peak detector will do is 28 µ-sec. If you will notice on my slide, A-weighting was specified. Weighting networks (A or C) degrade the meter to more closely match the response of the human ear. While I don't know exactly how bad the degradation is, I would guess it is to somewhere close to 25-30 µ-sec. In the video of testing the AAC can, they were using C-weighting, which is fairly similar to A-weighting in performance.

The comparisons I have done on firearm peaks show the LxT1 to read generally less than 2 dB lower than my 800B (which has a measured rise time of 13 µ-sec). However, the real test is unweighted. When unweighted (LD calls it Z-weighting), the LxT1 reads 6-7 dB below the 800B. Regardless, even the 800B (or 2209) misses the peak maximum even unweighted. The B&K Pulse misses less.

2 years ago, a B&K rep passed through Boise to demo to us a Pulse system. We compared it to the 800B, and our finding were that the 800B read only 1-2 dB low when weighted, but unweighted it was closer to 4 dB low. The Pulse theoretically has a rise time in the vicinity of 2 µ-sec, but the 1/4" pressure mic they had possessed a rise time of around 7 µ-sec according to the calibration curves with it. This means simply that the best system rise time could not be any better than the weakest link. My experience has been that some of the 1/4" pressure mics have worse response curves than others. For the Pulse system, one should use a 1/8" pressure mic, and the B&K rep did not show his product in the best possible light.

My experience using the 800B has been that the non-suppressed M4 (14.5" bbl) has a C-weighted SPL of 163-164 dB at the reference location, and a 10" bbl AR runs 167-168 at that location. The 20" barreled M16 runs 162.

Should we be doing SPL measurements unweighted? Of course -- it is the better indication of hearing damage risk. However, use of A- or C-weighting dates back to the mid-to-late 1970s when the 2209 first came out and the early pioneers (Finn, Knight, Walsh) decided the data looked better weighted. This resulted in the new MIL-STD-1472 either specifying or permitting the use of weighting and our industry adopted weighting.

Is the reference location the best place to measure? It is the best estimate of what the target will perceive. The shooter's ear is a better estimate for hearing damage risk, but we negate that benefit by using weighting. And it wasn't until relatively recently that the shooter's ear locations became defined as a specific location in space with reference to the back of the receiver.

Back to the testing video. There are some unanswered questions, and I think the measurements recorded are low. First would be whether the meter had been calibrated with a certified field calibrator (such as the LD CA250, or CA200 as a less accurate second choice). Second was the measurement location (reference, 2 meter spacing instead of 1, ear?). Before I left Gemtech, sound measurements were made on a permanent field jig that positioned the weapon properly and held the microphones on separate permanent locations referencing the muzzle. We also used the 800B. Since I left, I still measure that way and Gemtech is using an LxT1, although they have requested a Pulse from the Mother House.

I hope this helps. I am not an expert, but I have been playing with this stuff for a long time and I have gone through a tedious (and expensive) learning curve on sound measurements. In my opinion, the LxT1-QPR, while not quite as accurate as we would like, is better than most of the alternatives when used with weighting.'

Couldn't have said it better! It has always been my belief that the purpose of sound testing was in the product development process to measure progress. I have been opposed to marketing use simply because there are too many variables (ammo, weapon, location, phase of the moon, etc.), and in the past there has been questions of made up results. Regarding marketing usage, I was outvoted a number of years ago. For 5.56, we use M855 ball with an M4 carbine (14.5" bbl) and for .308 M80 ball usually on a 20" Remington 700.

Incidentally, regarding bullet flight noise, we measured 1 meter to the side of the flight path at 50 meters: 152 dB for M80 7.62NATO and 148 dB for M855 5.56NATO.

10mm_ asked "Which of these industry professionals make YouTube videos?"  So I listed a few that do videos using proper equipment.