.22 LDC bore clearance study print files
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Thanks, OldSpook
If better use of hardware is available via free or cheap software, then it is a no-brainer to use it.
I wonder if cheap or free sound level cellphone apps "do it right" for airgun report measurement.
If better use of hardware is available via free or cheap software, then it is a no-brainer to use it.
I wonder if cheap or free sound level cellphone apps "do it right" for airgun report measurement.
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After giving this some thought, you might get more realistic results if you are a little closer to the meter. I suspect that ambient noise levels fell either side of the rang of muzzle reports measured, and may have been messing with the relative reading process. To prevent that, the report of the quietest configuration needs to be louder than ambient. Also, to state the obvious, if a Harley or helicopter are passing by, wait for them to be gone before firing the shots.
If you have the time, motivation and energy, could you repeat the exercise with the meter 3 meters from your shooting position, rather than 5? This situation may be unusual, because you are shooting at a modest power level. For more potent airguns, the risk is usually "pegging" the meter by being too close.
Thank you for always being so eager to participate in these types of exercises. For AGN members, Mike has done a bunch more of these on GTA.
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Here are some interesting, related results to this experiment - but they do not use the printed moderators in this thread.
I was trying to decide on what to do to quiet down my .22 cal Sidewinder, and I ended up having the hardware to compare identical Huma 40 Compact moderators - one for .30 cal and one for .22 caliber (the .30 has a 9.0 mm exit hole, and the .22 has a 6.9 mm exit hole). The difference between the two, averaged over 5 shots, was only 1 dB on my phone app, and sounded no different to my ear.
Here is all the data, including on the "bare barrel" and the mod with added sections, plus the surprising results when I repeated the test on my Huben: https://www.airgunnation.com/thread...tor-for-a-22-sidewinder.1298720/#post-1600882
I was trying to decide on what to do to quiet down my .22 cal Sidewinder, and I ended up having the hardware to compare identical Huma 40 Compact moderators - one for .30 cal and one for .22 caliber (the .30 has a 9.0 mm exit hole, and the .22 has a 6.9 mm exit hole). The difference between the two, averaged over 5 shots, was only 1 dB on my phone app, and sounded no different to my ear.
Here is all the data, including on the "bare barrel" and the mod with added sections, plus the surprising results when I repeated the test on my Huben: https://www.airgunnation.com/thread...tor-for-a-22-sidewinder.1298720/#post-1600882
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Setup pix meter placed 3meters down range. Same Gun only shooting JSB Hades 15.89g@ 840 fps.
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OK 2 shots per bore test size. gun without moderation 97.2dB
8.5/ 95.7dB
7.5/96.7dB
6.6/96.2dB
8.5/ 95.7dB
7.5/96.7dB
6.6/96.2dB
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Had the 7.5 on my Gk1 works great! my next test checking which is quieter the 7.5 or my 25 offset 1.5x5.
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So your results show that the larger the exit the quieter the moderator?
Rather than being stuck on ranking the mufflers low to high, note how close the readings are. What I see from Mike's first and second set of results is that moderator bore size makes no practical difference, on his air rifle, with that tune (two pellet types, if I am not mistaken).
Placing the meter at 3 m instead of 5 brought all the readings up in a believable manner. So there is a real signal for when the sounds are actually louder.
I see noise in the readings, not a signal. The noise may be from variability in the air rifle; or the measurement system. In any event, a 1 dB range in sound level is meaningless, in my opinion. It is meaningless as a result, and it is meaningless as noise in measurements. Unless your mufflers reduce report by only 2 dB from bare muzzle. Then 1 dB more is everything.
Alan got similarly small signal for baffle bore diameters, and some "inversions" from what one might expect: https://www.airgunnation.com/thread...ator-for-a-22-sidewinder.1298720/post-1600882
As Paul Harrell likes to say, "not enough of a difference to make a difference". Certainly a smaller difference than I would have predicted, but as I am not concerned about sacrificing a 1 or 2 dB reduction for the sake of a more pleasing sound, or confidence that there will be no clipping due to poor alignment.
Hopefully more people will have a go at this so we have more results to consider. In any event, if anyone suggests skewed results due to poor equipment or technique, let them run their own test on these moderators and report their results. I welcome more consistent results, to see if there is a meaningful signal. What is meaningful to me may be different than the next person. So lets see some more numbers. Else, what we have will have to do.
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Yep. when it comes to my Gk1 the 6.5 is the quieter 98.4dB other 2 101.2dB. And against the 25 offset 1.5x 5 with a 95.7dB to the 6.5 with 98.4dB. I will be using the 6.5 on the Gk1 lol the 1.5x 5 weighs 91.71 grams the 6.5 28.35grams.So your results show that the larger the exit the quieter the moderator?
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Perhaps there is a difference in turbulence or standing waves that interact differently with baffle bore diameter, at different power levels.
MAC had a new suppressor testing video for a 9 mm can, released yesterday. He tried it on several pistols and carbines, with different bullet weights. In one instance a 16" barrel produced higher dB readings than a pistol. My immediate reaction was, "nonsense". But perhaps there are some effects that occur, apart from the basic, "a longer barrel has more expansion volume, so it will always be quieter" effect.
MAC had a new suppressor testing video for a 9 mm can, released yesterday. He tried it on several pistols and carbines, with different bullet weights. In one instance a 16" barrel produced higher dB readings than a pistol. My immediate reaction was, "nonsense". But perhaps there are some effects that occur, apart from the basic, "a longer barrel has more expansion volume, so it will always be quieter" effect.
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No. The error is within the standard deviation for the sensor. You can't get meaningful measurements to +/- one dB with a cell phone set up as a dB meter. If you need to take enough measurements to confirm that for yourselves, take fifteen or twenty measurements with the same setup and calculate the standard deviation. Then it will make sense to you.
Ok, lets explain that... So a dB meter AVERAGES its instantaneous readings over a period of time. That might be 1 second or 500 ms or 200 ms generally that is not known on most phone apps. The problem comes in when you pull the trigger at 0ms on one shot and say 100ms on the next shot. If your time slice was 250ms and you hit 0ms for your start on one shot, you would get almost all of the shot noise in the window on that shot. If your start time for the shot on the next slice was 100ms you would chop off 100ms of the shot noise on the back end of that slice. You would get a significantly lower reading for that shot. That is why dB meters don't work for people. You can mitigate that by taking a large number of samples and calculating the average and standard deviation. Most people don't want to bother with that additional effort.
This explains the complaint that so many make about dB meters not being accurate enough to do good studies. The complaint is half true. dB meters ARE accurate enough if you learn how to use them and then use them that way.
I talked about standard deviation in one of my posts a long time ago. Here it is.
So if you want to get accurate readings with a dB meter you should probably take 10 samples and compute the average and SD for those. Then you would have a "fairly" accurate measurement of what that moderator is doing on that setup. One reading is a crap shoot. Two readings is a wild assed guess. You can think if it like shooting groups. You REALLY want to know how your rifle groups? You are going to shoot a minimum of 10 shots AND do the math. Too much effort so we shoot multiple groups of five instead.
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