Taming the bark of an Avenger

[subscriber]

I was not far off when predicting the sound trace shapes, here:  https://www.gatewaytoairguns.org/GTA/index.php?topic=196584.msg156323244#msg156323244

At least with regards to the broad flat VS ramped shape; and how friendly they sound - compared to my previous post, on the bottom of the last page:

[JimD]

I agree that my ebay type device with the shroud holes gets lower ahead of muzzle measurements by increasing the measurements back by the shooter, me.  I don't see that as a bad thing for my situation because a couple buildings (my house and my neighbors pool house) are in the way of noise transmission from the shroud area but the downrange area is open.  But without measurements that is just my speculation, it could be the structures reflect the sound and make it more noticable.  Anyway, I still like it.  But a lot of that is the fact that it doesn't make my long gun any longer.

It might be possible to adjust the noise increase to the shooter with the number and size of the holes.  I drilled mine while messing with shroud baffles so I just simulated what I see on my P35.  If I was doing it now I would try 4.  That might give most of the down range improvement while not making the noise at the shooter as much louder. 

I bought my Tanto because I thought I could fill my gun without removing it.  That turned out to be true.  It is not a huge extra effort to take it off and in a better grade/temper of aluminum the threads would hold up better than my home made one did but I still see having to take it on and off as an undesirable attribute.  Steel threads should wear even better, however.  It also seems possible to have a 90 degree foster fitting but I've never seen one. 

[TorqueMaster]

Bob,

I was suggesting that leading edge of the sound, and how tall that vertical "flat section" there is, correlates with how harsh the "slap" sound of the shot is. 

Gotcha, that agrees with what I'm hearing.  And yeah, your crude waveforms make sense.  Avoiding abrupt changes should "sound better."

Any thoughts on the metallic "ping" at about a quarter second--  I just rechecked I'm a dope, it's 0.025-0.026 seconds -- in on all the samples?  It dominates the waveforms well after the initial "crack."  From reading, consensus is that regulated guns don't have reservoir ping, so I'm back to thinking it's the shroud.  In addition to a blanket, I may try clamping wood or somesuch to most of the length or just certain points along it's length to dampen the tubular bell.   I visualize, probably incorrectly, the air in the shroud bouncing back and forth, like a compression wave, venting more every time it's near the muzzle.  Venting some at the rear could help.  Partial cones or other disruptions in there could burn off that energy, too. 

I just did more listening, and looked at a spectogram -- the "metallic ping" sound is happening around 14-15,000 Hz.  *IF* I can hear that at all, it's probably the "pleasant" whoosh of air sound.  It's the most prominent single frequency in the whole discharge sound.  The "crack" is spread across the spectrum.  I'll add images.  very interesting.

JimD -- ok, I see where choosing where the sound exits can have overall benefits.  And am in agreement it's best to find an ldc that does not hamper filling, and can just stay on  -- from both wear and poi aspects.

[TorqueMaster]

  It also seems possible to have a 90 degree foster fitting but I've never seen one.

I think this is what you want?  Reply #3 has a link.

https://www.gatewaytoairguns.org/GTA/index.php?topic=180365.0

[WhatUPSbox?]

Any thoughts on the metallic "ping" at about a quarter second--  I just rechecked I'm a dope, it's 0.025-0.026 seconds -- in on all the samples?  It dominates the waveforms well after the initial "crack." 

I've been looking at that double peak separated by about 23-25 msec. Interestingly, looking at your 100 to 3 ft sequence, that second peak starts at about 25 msec and then moves closer to the start as you get closer to 3 ft, ending at about 9 msec. Is there anything in your test range that might give a reflection? 25 msec is fairly long as far as the shot cycle is concerned. Maybe hammer bounce releasing some air through an unobstructed barrel? Still, there is quite a bit of noise in that second peak.

[JimD]

Thanks for the link Bob.  Price seemed kind of high then I looked up what a 5,000 psi 90 degree elbow goes for.  McMaster Carr wants more than Air Tanks Plus charges for the entire fitting.  Their stuff is good too, that is where my fill set is from. 

[subscriber]

Bob,

The shroud tube could certainly ring from being thumped by the shot event.   If damping that with a blanket works, it would be an indicator that the tube is ringing.   The air inside could certainly have sound waves bouncing along the length, between shroud muzzle and barrel support; and barrel support and breech.   Perhaps Stan could calculate the natural frequency for an air tube (shroud) at a nominal ATM pressure, at the lengths corresponding to the front and rear shroud spaces?

Either way, I can't hear anything above 13 kHz anymore, so pings in your sound recording run at full speed must be below 13 kHz for me to hear them.  Slowing down replay may reveal more, but that seems like cheating to reveal a problem that is hidden.  That said, when I was in my mid 20s I could hear color TV screens buzz at 20 kHz.  I could hear them walking through the neighborhood outside houses.

With all three recordings, after the initial crack, I hear mostly a whooshing sound.  Something that is not unpleasant.  The crack is most obvious with the bare muzzle; with the eBay unit having a small one and the Plume almost completely absent.

[TorqueMaster]

Any thoughts on the metallic "ping" at about a quarter second--  I just rechecked I'm a dope, it's 0.025-0.026 seconds -- in on all the samples?  It dominates the waveforms well after the initial "crack." 

I've been looking at that double peak separated by about 23-25 msec. Interestingly, looking at your 100 to 3 ft sequence, that second peak starts at about 25 msec and then moves closer to the start as you get closer to 3 ft, ending at about 9 msec. Is there anything in your test range that might give a reflection? 25 msec is fairly long as far as the shot cycle is concerned. Maybe hammer bounce releasing some air through an unobstructed barrel? Still, there is quite a bit of noise in that second peak.

Very interesting observation!  Unfortunately, no.  I have my back to the house, so the muzzle is about 8-10 feet from that wall, and that distance *increases* as I walk forward.   There is also an outbuilding to my right, about 25 feet away, which I walk parallel to, then past it's end, so very unlikely it is adding any echo either.  There are trees around... one thing solid is the 1" aluminum pipe I have the phone perched atop.  A 25ms delay is about 28 feet added, 9ms about 10 feet added ... but I'm walking amost 100 feet during the test...nothing makes sense for it to echo off of.  Short of mapping this geometrically, it seems like the "wall" would need to be about 5 feet from the phone?  The closest object would be a small tree I pass at about 60 feet from the start, about 10 feet to the left, with metal fenceposts around it, and metal garden fencing (keep deer from eating bark) but it is very open weave, and posts quite thin, not much of a "wall..."  Numbers don't add up.

[TorqueMaster]

Thanks for the link Bob.  Price seemed kind of high then I looked up what a 5,000 psi 90 degree elbow goes for.  McMaster Carr wants more than Air Tanks Plus charges for the entire fitting.  Their stuff is good too, that is where my fill set is from.

Yes, pricey.  To be safe with this high pressure air is not cheap.  I was looking at Unions and tees for my pump, while not as bad as that elbow, still way higher than the typical 100psi parts.  You almost have to buy from someone you trust -- aliexpress or ebay etc play fast and loose with the "specs" if they even offer them.

[TorqueMaster]

Bob,

The shroud tube could certainly ring from being thumped by the shot event.   If damping that with a blanket works, it would be an indicator that the tube is ringing.   The air inside could certainly have sound waves bouncing along the length, between shroud muzzle and barrel support; and barrel support and breech.   Perhaps Stan could calculate the natural frequency for an air tube (shroud) at a nominal ATM pressure, at the lengths corresponding to the front and rear shroud spaces?

Either way, I can't hear anything above 13 kHz anymore, so pings in your sound recording run at full speed must be below 13 kHz for me to hear them.  Slowing down replay may reveal more, but that seems like cheating to reveal a problem that is hidden.  That said, when I was in my mid 20s I could hear color TV screens buzz at 20 kHz.  I could hear them walking through the neighborhood outside houses.

With all three recordings, after the initial crack, I hear mostly a whooshing sound.  Something that is not unpleasant.  The crack is most obvious with the bare muzzle; with the eBay unit having a small one and the Plume almost completely absent.

I recently rebuilt a wind chime -- from those resources I have the shroud tube at 400Hz give-or-take.

One of my posts has the recording at one tenth speed - you can hear the "ping" there.  Sounds metallic but at 14-15kHz, who knows.  Only a problem for the guy not wanting to spook pests (or children, lol.)  Not to burst your bubble, but NTSC whine is closer to 16kHz.  Used to bug me, too.  Ummteen concerts later...I always hear the whistling in quiet rooms, no tv required.

Given the spectrogram shows that second peak is so high pitched, it's likely a loud but short-lived "dog whistle" sound that is part of the whoosh...

[subscriber]

Not to burst your bubble, but NTSC whine is closer to 16kHz

If it makes any difference, the TV noise I head was PAL:  First 33 years of my life were spent back in the old country.  For further amusement, there was no broadcast TV until 1976.

My observation was that color TVs with cathode ray tubes made the squealing noise, while black and white TVs did not.   Both using a roof antenna. I was told that the sound was at 20 kHz by my older brother, and he generally had good sources for technical info.  Does not mean he was always right; although he certainly thought so. 

[subscriber]

So, a member printed my "Plume" Avenger LDC version that I posed here a while back.  He reported some clipping towards the front.  So, I have created a version of the design with a stepped bore.  The baffle ID values are in mm - shown in red below.  Remember that the printed holes will be perhaps 0.3 to 0.5 mm smaller than the CAD values shown in red.

Revised STL print file attached below as a ZIP file to reduce file size.

[Spin]

So, a member printed my "Plume" Avenger LDC version that I posed here a while back.  He reported some clipping towards the front.  So, I have created a version of the design with a stepped bore.  The baffle ID values are in mm - shown in red below.  Remember that the printed holes will be perhaps 0.3 to 0.5 mm smaller than the CAD values shown in red.

Revised STL print file attached below as a ZIP file to reduce file size.

I would dearly like to see this moderator abbreviated in front of the end of the shroud. As has been said the Avenger is a fairly long gun to begin and I'd love to see the forward end of it extend no further than 1 1/2" beyond the end of the shroud. Less length, weight, less chance of misalignment (clipping) and less barrel extension to be bouncing off limbs, trunks, brush etc. I own and have used them for some time. These are the monocore moderators featured on E-Bay and so far they have actually proved out to be the most successful with the exception of a Dony FX can which again is longer than I like. I've also tried 3 more printed styles. The monocore's however do not feature a centering integral screw in - out feature and they can be a pain when removing from the shroud particularly if it's inside is gummed up with lead dust and oil residue. At least one more baffle might make an improvement I'm pretty sure this would go over with quite a few other Avenger owners.

[subscriber]

Jerryy,

How about this Shorty version?

STL attached as zip file.

I have a plus two inch version.  Just need to dig it up.

[subscriber]

Avenger Shorty +2"

STL attached as zip file

[Dbez1]

I know the OP is specifically not interested in this solution, but others that read this thread may be. My .22 Avenger is the proverbial “mouse fart quiet” with the following setup:  Donnie FL adapter and a 7 and 7/8” Neil Clague LDC. Yes, this makes the rifle very long at 52”, but for those of us that shoot primarily from a rest, it doesn’t matter. As you can see from the photo, it doesn’t interfere with the air quick connect. A downside is that it’s expensive but no one knows I’m shooting and there’s no effect on accuracy. One of our dogs is gun shy, but he’ll lay down beside me when I’m shooting the Avenger. Also, if I miss a groundhog, I usually get a second shot. 🤔

[Spin]

Avenger Shorty +2"

STL attached as zip file

  OK, I guess the 2"plus has my full attention. Who do I need to talk to to get one! I've spent some pretty significant time searching for one or a similar design and come up dry so far.

[subscriber]

Jerryy,

I will send you a PM, pointing to an expert printer

[Robert 5mm]

Just got the longer "Plume" one designed by Subscriber - it is as quiet as my DonnyFl  adapter with a long moderator - super design work

[subscriber]

Glad to hear that, Robert.

And thanks to Bob (TorqueMaster) for printing it.  He does a really good job, if anyone else wants to contact him directly via PM, pointing to the particular design you want, as located in this thread.  Or PM me to prime the pump with Bob, if preferred.