Western .357 rattler and aftermarket moderator

[Frito169]

I'd say there is no way that meter is capturing the sound pressure level peak properly - that bare barreled shot would have to be way over 100 db, especially in tight with all that reflective material right next to it. So your perception is about all you can go by, since the numbers are not going to be helpful even on a relative basis.

All I can say is turned way up on power shooting 142 gn nsa slugs I can shoot from inside my bedroom out the window you can barely hear the gun. The loudest moment in the shot is by far the impact. I didn't believe my friend so had him shoot while I stood outside and sure enough it was super quiet. The way i look at it, this gun is not made for plinking in a populated area in your backyard but still very quiet considering the power output.

 

[OldSpook]

I finally got around to testing the new shroud/suppressor by Neil Clague. Not ideal conditions but gives an idea of the different sound levels for no suppression, factory suppression and after market suppression. I Set power to the lowest using FX 81g pellets since I live in a suburban neighborhood, again just looking for a comparison. These were the first shots I made with this rifle since I got it and I already have one issue I'll post after this. It's really hard to realize how loud this sounds from the video, it definitely sounds louder live. The factory suppressor is pretty much useless or no improvement at all. The after market is better but not as mush as I had hoped. Caveat, not that it makes that much difference on the lowest setting but I use helium in all my hunting rifles, just thought I would mention that so everything is up front. After comments come in I can re make under better conditions. Perhaps having the meter in front of the barrel next time, but I did want to see what the decibel level is from the shooters perspective. I can also post a better picture later.

Here is the data from your audio. The recording was "rough" there was whole lot of echo. The numbers indicate the NC isn't doing that bad a job but your sound meter is averaging the echos. Decibel to Percent Calculator The stock moderator is a 24% improvement over the bare rifle and the NC is a 37% improvement.

 

[OldSpook]

All I can say is turned way up on power shooting 142 gn nsa slugs I can shoot from inside my bedroom out the window you can barely hear the gun. The loudest moment in the shot is by far the impact. I didn't believe my friend so had him shoot while I stood outside and sure enough it was super quiet. The way i look at it, this gun is not made for plinking in a populated area in your backyard but still very quiet considering the power output.

Well your 12 gauge would sound pretty quiet from the same position. You know that right? You go stand by the target and neither would be very quiet.

 

[Frito169]

Well your 12 gauge would sound pretty quiet from the same position. You know that right? You go stand by the target and neither would be

Well your 12 gauge would sound pretty quiet from the same position. You know that right? You go stand by the target and neither would be very quiet.

Silliest thing I've ever heard. Sitting just outside the window of the room where the gun is fired not by target.

 

[Azycray]

Here is the data from your audio. The recording was "rough" there was whole lot of echo. The numbers indicate the NC isn't doing that bad a job but your sound meter is averaging the echos. Decibel to Percent Calculator The stock moderator is a 24% improvement over the bare rifle and the NC is a 37% improvement.

View attachment 424949

So what would the best way to set up another test? Position of meter to rifle and surroundings etc.? Power level and weight of slug etc. to tune for quiet? Looking for suggestions and I will do it over for more reliable results.

 

[OldSpook]

So what would the best way to set up another test? Position of meter to rifle and surroundings etc.? Power level and weight of slug etc. to tune for quiet? Looking for suggestions and I will do it over for more reliable results.

What you've got there is good enough. The results won't change much from what you got. Best place to test is an open field at least 25 yards from structures. Then keep the mic at some known distance and elevation AGL.

 

[WobblyHand]

@OldSpook are those signals clipped? Or are they simply right up to the edge? Hard to tell. Tough to get quality measurements that mean a lot with clipped signals. (Saying that as a retired radar engineer.) BTW, it appears to me that you are taking a methodical approach to this. Kudos to you. Seen a lot of seat of the pants engineering with things like this, so it's a breath of fresh air to see your approach.

I'm trying to make a "fixtured" sound setup so I can measure mine. Playing along with gyroidal fill and TPU. Seems to change the tone. I'm using regional meshing so the interior structures are gyroidal mesh, and the exterior structure is 100% infill. The resultant print is stiff enough on its own, and doesn't require a support tube, at least for the lower power testing that I have done. The slicing can all be done in PrusaSlicer, which it seems you are using.

Appreciate the work you are doing and your contribution towards better, high performance air gun moderators.

 

[OldSpook]

@OldSpook are those signals clipped? Or are they simply right up to the edge? Hard to tell. Tough to get quality measurements that mean a lot with clipped signals. (Saying that as a retired radar engineer.) BTW, it appears to me that you are taking a methodical approach to this. Kudos to you. Seen a lot of seat of the pants engineering with things like this, so it's a breath of fresh air to see your approach.

The microphone was at 5 yards @ 10:30 relative to the shooting position 3 feet off the ground. I used the Dolby ap on my Android phone to collect the audio. I exported the audio from the Dolby application on my Android phone to my Google drive and downloaded it onto my desktop. The phone was set up to record lossless audio as a WAV file. I then imported that file into the "Audacity" application and worked with the spectrum trace from there on out. First I tested for clipping and repaired that by attenuating the entire stream 0.5 dB at a time until I had removed the clipping. Then I chopped out all the signal trace except 100 ms for each shot. I started the cut with the sound of the trigger and chopped it at 100 ms. That is far longer than the muzzle blast itself which seems to be about 20 ms on most platforms. Most guns have a lock time around 10 ms and that could have been (but was not) chopped out. After 30 ms or so I think the vast majority of the noise is due to resonances in the guns themselves which seem to last another 20 or 30 ms before gradually dying down.

It would be good to work up a standard test methodology so that the engineers could compare apples to apples and share files.

I'm trying to make a "fixtured" sound setup so I can measure mine. Playing along with gyroidal fill and TPU. Seems to change the tone. I'm using regional meshing so the interior structures are gyroidal mesh, and the exterior structure is 100% infill. The resultant print is stiff enough on its own, and doesn't require a support tube, at least for the lower power testing that I have done. The slicing can all be done in PrusaSlicer, which it seems you are using.

Prusa slicer, yep, I like it. I did use Cura for a while and there's nothing wrong with it. I saw a thank you note to the Cura team from the Prusa people regarding their implementation of the gyroid infill code. It does change the tone and I'm doing something very similar to what you are describing but I am leaning towards carbon fiber because its a bit lighter and seems to limit transmission of vibrations from the moderator back to the barrel.

Appreciate the work you are doing and your contribution towards better, high performance air gun moderators.

I look forward to seeing your thoughts.

Mike

 

[WobblyHand]

Thanks for the technical update on your signal capture. That's helpful.

Up here in New England right now isn't conducive to much outdoor testing. When the weather moderates I can try something similar. I may try something indoors, but that will require some serious acoustic work, or some cleverness on my part to overcome the environmental issues (echo). Was thinking of rigging an acoustic tunnel, but that's just a bit of a pipe dream at the moment. In my work life I've made anechoic chambers, but hey, there were budgets for that.

The properties of carbon fiber are attractive from quite a few perspectives. But for fooling around, it didn't make sense for me to source relatively large diameter CF tubing, at least not until my design(s) warranted the investment. I did get some small CF tubing (25mm OD/ 22mm ID) and was able to thread the inside diameter fairly reliably on my lathe. Coupled with matched machined aluminum end caps, it makes a nice looking, rugged moderator.

For giggles and grins, I did a test fire with a gyroid infill moderator indoors. This was with a iMM-6 calibrated Measurement microphone connected to Audacity on my PC. I adjusted the microphone gain until there was no clipping. (1/8 volume, what ever that is!) Microphone was only 0.5m away from the LDC muzzle.

I just did this to look at the acoustics of the room. Nothing is calibrated relative to an unmuffled shot. What I did see was an exponential ring down of the envelope, as well as an echo corresponding to one of the walls. (@ 28ms) I wrote a python script to plot the graph below. First trace is simply the amplitude vs time, second is the magnitude vs time, third is the power expressed in dB's vs time. The straight line in dB's (for a long time) is the exponential decay of the signal. It's hard to recognize in the linear domain, but it's real obvious in the dB domain.


Here's the wav file if you are interested.

 

[allinssd]

All I can say is turned way up on power shooting 142 gn nsa slugs I can shoot from inside my bedroom out the window you can barely hear the gun. The loudest moment in the shot is by far the impact. I didn't believe my friend so had him shoot while I stood outside and sure enough it was super quiet. The way i look at it, this gun is not made for plinking in a populated area in your backyard but still very quiet considering the power output.

If I shoot full power with the factory mod I need ears, otherwise my ears are ringing like hell.

 

[peterj59]

When did the rattlers come with cf barrel shroud?