Noise Level: .30 Cal vs .22 Cal

It would be useful to see some comparative videos of different "quiet" airguns being fired, where the sound level is fixed, and with the mic is at the same distance and direction, but far enough away to ensure there is no clipping. Also, far enough away from the trap, so that impact noise does not dominate. Or something like this:



Nail guns, the whole lot of em. You're not getting an airgun quieter than that t50 stapler even that thing packs a punch to my eardrum!
 
Beware overly broad absolute statements. Here are two user accounts of very quiet PCPs; that I happened to have designed replacement baffles for:
https://www.gatewaytoairguns.org/GTA/index.php?topic=206735.msg156438137#msg156438137 :

Thanks Bob! Yep, took it out last night after installing it and shot a couple shots into the woods behind the house. The only sound was the tap of the hammeer on the valve poppet! I had to check the fill pressure because it sounded so weak, but no, it had a full 250 BAR filll! I then shot a couple rounds at my target, the pellet hitting the backstop was way louder than any sound coming from the gun! It's scary how quiet it is now... The perfect stealthy pest carbine! ;D

YOURS is broken too? Those backstops just keep getting LOUDER and LOUDER!

The Notos is not a very potent PCP, but it may be quieter than a stapler, after a little help. That said, I agree that making a 30+ FPE .22 or 40+ FPE .25 near "silent" is near impossible. Assuming it has a typical 20" barrel, and not something much longer. An airgun does not need to be silent to be useful. It just needs to not draw unwanted attention from someone in the next room, or the next house.
 
Beware overly broad absolute statements. Here are two user accounts of very quiet PCPs; that I happened to have designed replacement baffles for:
https://www.gatewaytoairguns.org/GTA/index.php?topic=206735.msg156438137#msg156438137 :

Thanks Bob! Yep, took it out last night after installing it and shot a couple shots into the woods behind the house. The only sound was the tap of the hammeer on the valve poppet! I had to check the fill pressure because it sounded so weak, but no, it had a full 250 BAR filll! I then shot a couple rounds at my target, the pellet hitting the backstop was way louder than any sound coming from the gun! It's scary how quiet it is now... The perfect stealthy pest carbine! ;D

YOURS is broken too? Those backstops just keep getting LOUDER and LOUDER!

The Notos is not a very potent PCP, but it may be quieter than a stapler, after a little help. That said, I agree that making a 30+ FPE .22 or 40+ FPE .25 near "silent" is near impossible. Assuming it has a typical 20" barrel, and not something much longer. An airgun does not need to be silent to be useful. It just needs to not draw unwanted attention from someone in the next room, or the next house.

Video of the notos being quieter than a t50 stapler?

You can certainly detune a pcp enough to where its action and muzzle exit is quieter than a stapler, but these are NOT ideal conditions nor typical...as shooting pellets at 200-300 fps is not generally viable for any use other than to say, I shot a pellet quieter than a stapler...
 
I wish I had a video of the Notos compared to a stapler. So, I admit that I am speculating, based on two people using my LDC insert design both claim that the hammer strike of their Notos is louder than the muzzle blast. This with the factory tune on both Notos', delivering 12 to 13 FPE. Not 200 or 300 FPS.

I never take peoples words for mouse fart quiet pre-charged pneumatically actuated rifles, videos always tell another tale. People make wild claims online that never make it to light in video...

my 20" barrel with a very big 8" ldc still is loud at 12-13 fpe...certainly is quietest at 12 fpe in .25 compared to 12 fpe in .177....that is because the pellet is heavier and moving much slower upon exiting the muzzle...which means slower moving air behind the pellet...
 
I agree that sound level is highly subjective. I am skeptical about people I don't know. That thread about the Notos does have some measurements in it, that one could also question. There is more signal to noise on a GTA thread entitled, "Taming the bark of an Avenger". From that it seems that getting any 30 FPE .22 cal PCP report below 75 db is very difficult. The claims were that the Notos were well below 70 db, but it was a different person capturing it.

From my perspective, if someone asks me to design an LDC and they are happy with the result that is what matters to me. My most popular baffle design is not necessarily quieter than DonnyFL products of similar size, but people often prefer mine because the initial crack is very much subdued.

If your have a 20" barrel 12 FPE PCP with an 8" long LDC that is still loud, it should be easy to improve on that. If you like, I will design a custom LDC for you to try out. What OD is this LDC? What mounting thread is on the PCP? Feel free to send me a PM, and I will design a super quiet LDC for you that is no larger than the one you are using - providing it is at least an inch in OD. You trust you own ears and measurement methods, don't you?
 
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Stubbers,

I had an idea that might be more convincing for you, based on this claim: That your 12 FPE PCP can be quietened down to where you are aware of the hammer strike when you shoot it, rather than the muzzle blast:

Rather than a completely new LDC design, I propose taking my existing custom Notos insert design and adapting that to form a self contained LDC, that would have the same installed configuration as the Notos guys claim is super quiet. That way, you are getting what they have, from a functional point of view, except that their barrel length is less than 12", compared to your 20". Should be fun.

Below is a section image of my Noto custom insert. The blue lines represent material I would add to turn it into a self-contained LDC, as you won't have a Notos shaped cavity to place it into. I would add a female thread of whatever diameter and pitch you like to mount it.

You made a statement that such a level of quiet was not possible, unless the PCP was detuned to 200 or 300 FPS. I wish to have you put that to the test. I would be happy to send you the STL file to print a part that looks like the combined image below. Then it will be up to you to test it and report back. In fact, I extend this offer to any interested party that has a "civilized" posting history.

Note that this insert was designed for low power .22 caliber PCPs. The baffle cone walls are thin, to maximize internal volume. If your tune is above 30 fpe there may be some question as to its durability - depending on the material choice and layer to layer integrity of your print. It should be fairly quiet though, compared to similar size devices at similar FPE.

What say you?

Modified custom Notos insert.JPG




For those who want to see my posting history to determine if it is civilized, this may help:
www.gatewaytoairguns.org/GTA/index.php?action=profile;area=showposts;u=27877

If you are not a GTA member then the screen capture below will have to suffice:

GTA profile.JPG
 
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So, an almost square wave, opening and closing action. Sounds like balanced valves are the way to go for performance and efficiency.

I assume they are too expensive for most PCP manufacturers to use; and one does not want a "cheap" version.
Not really that much more expensive ... Just a WHOLE LOT HARDER to get the tune correct in that of Wanted Power, Hammers weight & stroke, strike energy against valve etc ... While they offer a HUGE swing in output power one can adjust, it takes far more fiddling with with a steep learning curve in cause & effect. THEY are VERY very pressure sensitive and generally once they are is adjusted correctly, simply changing plenum pressure ramps power up/down quite a lot.
THEY DON'T ACT or ADJUST like a conventional poppet valve. Little changes can have valve swing the tune its at wildly.

While a FX impact uses a NON pressure feed back balanced valve, it too has many adjustments in play to get it settled in at a specific output / pellet / slug etc

For a manufacturer & a buying public a balanced valves only real advantage is high output with minimal opening energy required making it easier to extract big power w/o use of *heavy hammers and massive springs. *That creates harder cocking, more shot vibration and more wear on trigger components & the like.

Lower power PCP's really are better served with a conventional valve IMO
 
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OK. I have created self contained versions of the extended Notos insert above, for general consumption. One version sports a 1/2 - 20 UNF thread, and the other a 13/16 - 28 thread.

I can't make it any easier than this. Unless you have tried this muffler on your 12 FPE Marauder, Stubbers, don't tell us that a PCP can't be so quiet that the hammer drop is louder to the shooter than the muzzle blast, at this power level and barrel length.

You can download the STL files from the link below, but will need to be logged in as a GTA Forum member: www.gatewaytoairguns.org/GTA/index.php?topic=208202.msg156450425#msg156450425

(if you are not a GTA member, I can email the STL files to you)

If you are logged in on GTA, the page will look like the image below. See red arrows for STL download links:

Download file link image capture.JPG
 
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I have a FX Impact manufactured right before the 2nd version came out. Originally it was a .30 cal with 600mm barrel. Changed it to .22 with 600mm barrel. Both had the same Donny FL LDC. When pesting around the house the residents didn't know I was shooting with the .22. The .30 was too loud so only shot when the house was empty.
 
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Thanks Matthias,

I try to be concise, then usually end up with twice a reasonable word count.

You may quote anything posted on a public forum without permission. My thoughts included. Some people are sticky about attribution. I am not.

If you quote a person by name and want to cut out irrelevant text, be careful not to change the original meaning, or context. Else, I think that editing out superfluous text makes the re-post stronger.
Subscriber, I could use a distillation of your comments, if you don't mind. I have been reading for a while now, and I am tired, so that my be it. I am very concerned with noise reduction. I am also curious why Motorhead's .30 is so quiet. I have tended to shy away from the .30 due to my perception that the noice was much greater than the three main calibers under it. Thanks. S7
 
Sanctify7,

Are you asking me to be succinct? That is somewhere between impossible and torture :)

There are a number of overlapping factors that predict which caliber would be quieter. The same factor does not always dominate. An attempt to oversimply with blanket statements of an absolute nature are not helpful.

As an introduction to the answer to your question; you do not need to drive a .30 as hard to make a given FPE as you do to get that from a .25 or .22. This is because the larger base area of the projectile delivers more force at a given air pressure - assuming you can flow enough air. "Driving hard" has to do with the percentage of maximum power that platform could deliver in that caliber, and with that projectile weight. Part of the equation is about how wide the flow area is, and how long the valve is wide open.

If you run any PCP close to its maximum power it will become louder. With a .30 you do not need to run it very hard to make significant power. But, if you run a .30 as hard as you need to run your typical .25 or .22, then the .30 will make much more power and more noise.

If your regulator setting or air tank pressure is low (1000 PSI or less), and you insist on making lots of power, then the only way to achieve that, is for the valve to stay open much longer. This will result in the muzzle pressure being higher, which will make more noise.

I think I am already repeating myself. I desperately want to draw charts of air pressure decay curves inside PCP barrels. Rather than do that, I suggest you read the threads below. They cover this topic clearly, with plenty of graphs; with calculated or measured data - rather than blanket statement about complex conditional interactions:

Maximizing power for a minimal noise level:


Acceleration and velocity of a pellet inside a PCP:


EDIT: One more thing that is often not considered; the larger and heavier the projectile, and the more energy it carries, the more noise it makes when it hits the target - or whatever is behind the target. That could be a reason not to plink or pest with a .30 in urban areas. But, it makes sense for larger critters, or longer range shooting - assuming projectiles with a better BC than the smaller calibers. The latter is not a given: .22 slugs tend to have a higher BC than .30 pellets, for example.
 
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