20 Silencer Test

[rknobbe]

I have a 2020 AEA HP SS (.22). I just wanted to say thanks to this ongoing evaluation and the discussion here, I bought a threaded shroud and adapter from SurvivalAirguns and a DonnyFL Sumo from ThePelletShop.  Couldn't be happier with the sound and the accuracy.  Thank you for doing this thread!

[rkr]

I found an old silencer comparison that I saved from the old BSAOG forum. Compares most of the commercially available silencers in UK few years back:

[JungleShooter]

Cool! 👍🏼

I take it that the x-axis is time in ms? What is the y-axis?

Is there a link to see the test protocol and result data (cal., power, etc.)?

Matthias

[Madd Hatter]

I wish Geo was still selling the hunter. It was really quite but I had to take it out of the shroud to do something with the barrel and broke it. I never sanded it down like the instructions said to do so it was entirely my fault.

[subscriber]

I take it that the x-axis is time in ms? What is the y-axis?

Matthias,

The way I read the chart is that the Y-axis is sound level, or relative attenuation; and the X-axis sound frequency.  I say that because the peak reading with no silencer is the reference value at zero.  Also, higher frequencies drop off faster than lower ones, and the bare barrel traces are the loudest.

I think the chart could be truncated from 20 kHz and up.  20 kHz is the highest frequency most people can detect until their mid twenties.   My hearing cuts of at 13.5 kHz, meaning the sound level above that is largely irrelevant to me.   So, I ignore data above that.

The chart suggest that the silencers tested were very similar in performance.   Perhaps rescaling it to include only the suppressed sounds would highlight the differences more clearly.  Then the fact that dB is a log scale, and that human perception is non-linear could be factored in.

[Jshooter71]

I wish Geo was still selling the hunter. It was really quite but I had to take it out of the shroud to do something with the barrel and broke it. I never sanded it down like the instructions said to do so it was entirely my fault.

Shame… I wish he was still making them too. I could use a few more.

[JungleShooter]

Wow, Peter, you know so much more about so many things than I do — cool! 👍🏼

Thanks for the explain.
I'm always on the lookout for comparative silencer tests that will give us a better idea which models (or which types/ volumes/ lengths) are likely to work best for our personal applications.


🔶 An aside: 
Why does FX (and many other PCP manufacturers) make shrouds so THIN?!?  That way they are (1) flimsy (flop around like a noodle, esp. with a 700mm barrel) — and to the point of this thread — (2) they can gobble up less air, especially with the enormous power that the increased plenums and other power-pixie-dust are now producing.... Did the mfctrs. test this thin shroud and saw no major improvement in sound supression with thicker shrouds? ❓

(3) Also, did I mention bigger diameter barrels/ shrouds look better (to me, at least). When Huma created the "Hornet" — their 2" dia. mega-monster silencer specifically fitted to the Impact and the Leshiy 2 — it seems like they felt the same. 😊


Matthias

[subscriber]

Matthias,

I would never claim to know more than anyone else.  I just have a particular approach towards making sense of things that is rather intense.  I look for specific clues to help me identify the key that unlocks the rest of the data.

I can only speculate about the FX shrouds.  You know that they are developing CF barrel stiffeners that replace their flimsy shrouds?  These are used with large screw-on LDCs.

One reason to make the shroud "thin" is weight reduction.  But the added weight of a larger thin wall tube may be worth it: 

Now 1.5" may seem "fat" compared to 1".  However, its weight increase is proportional, as in 1.5 times higher (for the same length); while its volume is 2.25 times higher (less barrel volume).  And barrel outside volume is more significant with smaller shroud diameters.   I could calculate this for specific barrel ODs, but am just trying to make a point in principle. 

The increase in shroud stiffness should be about 8 times higher when comparing 38 mm against 25 mm with the same wall thickness.

At what shroud ID does the airgun look silly?  That is a matter of opinion.  The longer the barrel, the wider the shroud could be before looking odd.  Now, in my opinion, having a fat LDC at the end of a slender barrel or shroud looks odd

A wider shroud with a more sophisticated air stripper would make a huge difference in overall performance.  The larger the space between shroud ID and barrel OD, the easier it would be to make the stripper effective (and the whole system).  Not only for sending air to the rear of the shroud, but in protecting the base of the projectile from wobble inducing muzzle blast.  If you are interested, I will email you a recent design I did to illustrate a design intended to achieve both aims.

Often the question why design, manufacturing or material shortcuts appear to be taken, can be answered thus:  To reduce costs, while achieving "good enough" results.

[subscriber]

There is another consideration, Matthias

While increasing the OD of a shroud makes it stiffer along its length, eventually the shroud will lack stiffness across its diameter.  This could make the shroud more susceptible to ringing like bell at an audible frequency after the shot; and dent if knocked or pushed against an edge or pointy object.   This is, unless the wall thickness is increased (or wall depth is increased by swaging or pressing in fluting, for example.  Flutes could be in the original extrusion, but the ends will need to be formed back to round for threaded fittings).   

[rkr]

I take it that the x-axis is time in ms? What is the y-axis?

Matthias,

The way I read the chart is that the Y-axis is sound level, or relative attenuation; and the X-axis sound frequency.  I say that because the peak reading with no silencer is the reference value at zero.  Also, higher frequencies drop off faster than lower ones, and the bare barrel traces are the loudest.

I think the chart could be truncated from 20 kHz and up.  20 kHz is the highest frequency most people can detect until their mid twenties.   My hearing cuts of at 13.5 kHz, meaning the sound level above that is largely irrelevant to me.   So, I ignore data above that.

The chart suggest that the silencers tested were very similar in performance.   Perhaps rescaling it to include only the suppressed sounds would highlight the differences more clearly.  Then the fact that dB is a log scale, and that human perception is non-linear could be factored in.

You sir know your stuff, correct on all accounts. The lower the peak the better the silencer and measurements were taken up to 50kHz for hunters as quarry can hear high frequencies. Rancid Tom's modified Hogan was the best they measured and HW and Hugget were also very good. Here's the link to a thread that made me dig up that test: https://www.airgunforum.co.uk/community/index.php?threads/question-for-those-that-test-moderators.371991/page-2

[subscriber]

Thanks rkr,

Your point about animal hearing is an important one.  I am so focused on not upsetting neighbors that I forgot about animals in the field.

How far does sound at 50 kHz travel?  My feeling is not very far.  Especially if there is vegetation.  As long as at the expected range to quarry, the residual sound is lower than the level that would trigger them to run at that distance.

My theory is that prey animals are especially sensitive to the sound of a twig snapping, when it is stepped on by a predator.  So are humans.  So, the more "snappy" a gunshot sounds, the more attention it grabs.  Other sounds that grab attention would be growls and grunts, although those are more to warn intruders off, or call for mates.  A predator does not vocalize when it is stalking prey.  It just lunges and bites, usually from behind.

Now, if you could make a silencer that converts gunshot sounds from a snap/pop to the mating call of your intended quarry, it might draw them in, rather than chase them off

[subscriber]

I see that my questions were answered by your link, rkr.  Should have read that first.

Interesting that a rubber sleeve cut ultrasonic noise from the shroud tube in half.  I have advocated the application of vibration absorbing material such as that show below to shrouds and LDC, because the metal tube acts like a speaker:  www.amazon.com/gp/product/B01KZ5X7KO/

Below is a demo of the noise reduction seen when above material is applied to thin metal plate.  Should work as well on metal tubes.  (I suggest you reduce the volume setting before playing video):
https://m.media-amazon.com/images/S/vse-vms-transcoding-artifact-us-east-1-prod/v2/3255bca3-1dd6-53ab-bf75-a1b586df7ed6/ShortForm-Generic-480p-16-9-1409173089793-rpcbe5.mp4

[rkr]

I see that my questions were answered by your link, rkr.  Should have read that first.

Interesting that a rubber sleeve cut ultrasonic noise from the shroud tube in half.  I have advocated the application of vibration absorbing material such as that show below to shrouds and LDC, because the metal tube acts like a speaker:  www.amazon.com/gp/product/B01KZ5X7KO/

Below is a demo of the noise reduction seen when above material is applied to thin metal plate.  Should work as well on metal tubes.  (I suggest you reduce the volume setting before playing video):

One way of suppressing the higher frequency ping is to use elastic rust prevention spray on the outside of the silencer. Works well and looks quite OK:

pup-final-2_zps07b31a0d by abbababbaccc, on Flickr

[WhatUPSbox?]

Your point about animal hearing is an important one.  I am so focused on not upsetting neighbors that I forgot about animals in the field.

Some data. https://acousticstoday.org/wp-content/uploads/2016/01/The-Evolution-of-Mammalian-Sound-Localization.pdf

The problem with just looking at frequency is that, at least for humans, your ability to hear short duration sounds falls off as the duration drops below 200 millisec. An airgun sound is much shorter.
The second image shows a shot from my P17. Most of the higher amplitude is within the first 10 millisec

rkr, Thanks for the link. It mentioned another piece of sound software to play with. 

[subscriber]

Thanks for the interesting info, Stan

Directional hearing is important, if it is going to trigger the flight reflex; else prey may run towards the predator, rather than away.

My observation is that the local cottontails freeze when they hear a noise.  If the disturbance is over their threshold, the rabbits bolt, but only run about 20 feet before freezing again.  I assume they are trying to create distance, but stop to listen.  They want to know if the predator is following them, and can't hear properly when they are making noise while running.  Also, running draws attention - many animals move in burst to avoid their motion being seen.  Running is in effect announcing to predators that you are prey.  This is why humans should not run from aggressive dogs (or lions).

The cottontails that visit my yard will let me approach within 15 feet before bolting.  Some are habituated and allow me to get closer.  What makes them dash out of my yard to over 50 yards away, is if I drag my shoe sole on the paving to produce a multi-spectrum  "gggggk" sound.  These silly critters think they are invisible of they don't move.  Meanwhile, humans are also good at spotting form.  Some better than others.

A airgun shot sound may be short, but it tends to echo, depending on what is near the source.  Of course, the echo could confuse the location.  My point is that the total sound duration and pattern are also important.  As for sound frequency, a single sharp event (square wave) such as a shot produces a wide spectrum of sound frequencies from multiple sources:  If you slap and oil drum with a length of two by four, you make the drum and wood ring at their natural frequencies.  Since you struck one blow, there is no frequency to the event that cause the sound.  However, if the event is repeated that makes it much easier to identify and locate.

If you watch a dog's ears and its attention, they trigger on sounds we can't hear, or think insignificant.  Then listen actively for more clues as to what and where the disturbance is.  We do this too, in that a single airgun shot may trigger our attention, but not be perceived as significant.  It is when the person starts to actively listen that they are more sensitive to identifying and locating more shots, should there be any.

We recognize the sound of something like a spring air rifle, not just for its loudness (if close by), but for the cyclic nature of the cocking and shooting sounds at short intervals - if the person is target shooting or plinking, as opposed to hunting. 

Likewise, if you live out in the country hearing gunshot may not be especially significant.  When I hear them, I freeze to listen (unless I think that I am at risk).  If there are more shots, and they all sound the same, then the person is shooting in a particular direction.  If the person is shooting in random directions the sound changes.  Then the risk of them shooting you accidentally goes up. 

If I hear a snap followed by the pop of muzzle blast (with or without lingering echo), they are shooting towards me with something that is still supersonic when it passes by.  That is a clear sign to find cover, even if you are not the intended target.  People who have been shot at know the difference in sound between incoming and outgoing.  Vets reading this may be nodding their heads.

[Airgunshooter1]

Rick67 where please tell me!  I have been reading for hours now trying to figure out where to buy that one.  Why is it so hard to figure out. Everyone is talking about the suppressors and their results but poor ole me can't figure out how to find out this information. Just post it for us clueless old people.

[Airgunshooter1]

Where? my god it's so hard to find information here.  Where can I buy a A.U.O.?

[subscriber]

Where can I buy a A.U.O.?

Perhaps if you PM the person posting about that device, they could inform you as to its availability.  You may be out of luck:

they are down to their last 20 units or so with no plans to make any more.

[subscriber]

At the risk of emphasizing the obvious; suppressing ultrasound so animals are not spooked by the shot, matters more for culling, shooting pests/vermin, and such occasions where there are no bag limits (or more than one animal per day).



 

[subscriber]

Kern,

I don't know what airgun you want to suppress, but this recent thread may be useful to you:
https://www.gatewaytoairguns.org/GTA/index.php?topic=196584.msg156289805#msg156289805

Leading to this:  $16 to $25 Airgun Suppressors


Sold here:  https://buck-rail.com/product/air-venturi-avenger-suppressor/

Also see:  https://buck-rail.com/blog/