Sound Reduction.

[fangsnatcher]

Re: Sound Reduction.

memory foam also works well i'm told as is compresses nicely into all the voids in the rifle

[jonny lovegrove]

Re: Sound Reduction.

you know i never thought of memory foam, i have offcuts from my mattress... hmm.

[Chas]

Re: Sound Reduction.

It is time consuming and requires adjustment for each insert, not to mention lining the barrel up straight with your main barrel. However, it is very effective.
Design is similar to this H&K MP5SD cross section:



Yup, I a fortunate enough to be able to machine my own baffles precisely to 6 mm in tht very design.
I actually use a CF shroud, which allows for maximum sound to be reflected back into the silencer VERY effectively.
never tried memory foam, will have to try some soon.

[jonny lovegrove]

Re: Sound Reduction.

right, copypaste time. this is a big post. (sorry if there are broken rules here! i didnt write this!! and dont have time to read it all.)

Well here's the guide :tup:
What you need:

A Rifle (Preferably type 96)
High density foam (like in memory pillows) Or just the regular cheap foam will do fine. (get anywhere)
Another spring for your gun or just use the original. (This depends whether or not you want to cut your spring)
Plastic milk container or similar material
Ductape, electrical tape and telefon tape.
Hotglue/superglue (not essential)
Scissors/Knife.
Locktite.
Some sort of silicon grip for a wii or something like that. (Dealextreme and similar china wholesale sites have them for a dollar or 2)
And the tools necessary to take apart your gun of course ^.^


Let's start off with the silencer (If you have one)
---If you don't I recommend making one.
It's rather simple, just a piece of 2 inch or whatever you desire, radius PVC piping and two caps for the end. Then just a way to attach it.
(And painting or wrapping it would be a good idea)
I'll be showing you what to put in them later in the tutorial---

These generally perform poorly, but we can improve on that.


Here's my gun. See the silencer up the front? Screw that off. Then screw off the bottom part.


You should then get something like this or it may be empty.


Now, take out all the foam inside unless there is none.


Now this is where the plastic milk carton comes in.


Basically cut circular pieces the same diameter as the silencer and the cut holes in the middle slightly bigger than a bb. It's important you have it in a similar order to mine, as in don't have a spacer first have it like so: foam then spacer, foam then spacer, foam then spacer, foam and then then spacer last.



See? You can sort of see the spacer is last


I don't have images included but you should also replace the foam supplied with the silencer with foam of your own. High density foam etc. is generally much better then the supplied stuff. I have seen a significant change in pitch by using better foam.

TIP - Supposedly using a combination of coarse and fine foam works best. as in Coarse, fine, coarse etc.

Alright what's next? Ahh, the bipod. This one's simple but handy :yup:

Just wrap a tiny bit of Ductape around the part that locks into the gun. This will reduce the noise of the thing wobbling quite a lot.


Now, see the little allen screw on top of the tri-rail? Un-screw it and put on some locktite because it comes loose constantly and that causes rattling. You can thank me later


Now, another small modification for those using a full sized spring (You'll get what I mean later on)

You need some sort of soft silicon like a grip for a wii remote.


Then you cut it and super glue it to your cylinder head. Don't put on too much and don't, whatever you do put it on your piston head. It just slows down the piston (Friction etc.) and stops your gun from shooting and gets bashed up and comes off quite easily. Some are successful at this, but I am just giving you my experience >



Alright then here are the two more major mods. I'll do the foam one first. The foam mod works because much of the noise coming from your gun when you fire is actually the body rattling. Adding foam helps to stop this rattling.

For this all you need is foam and scissors. Oh and something long, hard and thin, such as a long allen key or screwdriver etc. (Nothing else to those of you who are dirty minded :lame: joke...)

I used that memory foam pillow because it is very high density and shrinks to a small size but then expands again. You can use normal foam too though I just find this works best.


This mod is really simple. Just cut it up into small pieces and shove it into empty spaces in your gun with the allen key until it can't hold any more. Make sure it's good and tight or else it won't work properly. Also make sure it doesn't go over the screw holes, magazine port, trigger port etc.

Just take apart the gun. The top and bottom part. The cheek rest and the buttstock.


And just stick in as much as possible into the but stock and super glue some into the cheek rest. The more the merrier!!




Then push in as much as possible into these gaps. Remember to cut the foam into small pieces so you can fit more in.




Then super glue some to the top where the barrel rests. Also glue some to where the trigger rests and on the trigger and bolt housing itself.



Now here is the last mod. This mod isn't possible for everyone to do. You need to have a Chronograph or be at a place where you can use one.


I live in Ireland where the power limit is 1 joule. The spring I received with my gun was over that so I had to cut it down. Results may vary :P

If you are buying a more powerful spring for the sake of cutting it down to your power (just quieter) make sure your sears and triggerbox can take it. As a more powerful spring will still have a similar compressing force even if it's cut!!!

Firstly you need a spring which is above your desired power. I have a 450 fps one which came with the gun and an upgrade kit one which shoots 485 fps. So I cut the 450 fps one.... and quite a lot for that matter to get the 328 I was looking for.

Alright firstly take out your bolt. Ignore the electrical tape and pull down that thing in front of the trigger. Also take off the cheek rest first.



Alright now you have this.


Un-screw the Cylinder head.

Now take out the piston and spring.
The one on the left is the one which came with the gun and it's cut. The middle one is the normal sized one. And ignore the one on the right. I just used a multi-tool to cut the spring.

Now cut the spring one or two rings at a time (maybe 3 if you live dangerously) and put back together the gun and chrono it. Keep cutting the spring one ring at a time until the desired FPS is reached. Only cut it a few coils at a time. Cutting a spring in half won't half it's power.... they don't work like that :ashamed:


Now see how far down my piston is. When fired the piston never actually hits the cylinder head thus creating very little noise.

When you put back together your gun you gun you may need tape to keep your bolt release in, the thing in front of your trigger.





Tips and tricks

1 - If it rattles tape it!
Some people even tape the bottom of the spring guide to keep the spring from rattling.

2 - Keep your gun lubed not only for performance, air seal etc. but it also keeps it much quieter.

3 - Try to use good springs like PDI ones that don't lose FPS/consistency and have easier draws. They will naturally make less noise. IMO don't ever get tapered springs unless made by a reputable company.

4 - Make sure to keep your O-rings lubed if you can but not over lubed. Silicon grease is best, but don't apply too much or any to the piston head. (Past the o-ring)

5 - I don't have need for one so that is why I haven't made one but if your are to make an airbrake be very careful. You can mess up your piston and scratch the inside of your cylinder if made wrong. However if they are made right, mother of god you can have a quiet gun :shot:

6 - Downgrading your spring will naturally make your gun quieter but with a lower FPS, if the Mods are done right you can still have a significantly quieter than average gun.

7 - Make sure all your screws are good and tight (But not over tight so as to not damage your gun)

8 - When making the silencer a good combo is to use different types of foam, such as - Coarse foam, fine foam etc. The combo will help improve sound absorption.

9 - MAKE BARREL SPACERS. Even if you buy them make some more of your own. In combination with a Steel barrel the vibrations will be cut down immensely, causing better accuracy and a quieter gun.

Now your done. Hopefully these mods will help you be the Ghillie in the mist we all aspire to be.... or already are
These can all be done with a stock gun as well. So combine this with the plethora of other stock mods and you can have one fine gun!

Here's my gun as it is now, with a better home-made lightweight silencer, changed out internals, and quieter than ever.

Now your the silent killer

[Another]

Re: Sound Reduction.

If we're talking about Foam, I'll bite. I work with technical foams as part of my work.

Reticulated foam is actually isn't the best for sound reduction. This is because 97% (give or take) of the foam's cell structures are purposely burst during manufacture which allows fluid and air a great degree of freedom to pass through the foam. Sounds travels by air vibration, easy movement = less absorption.

Memory foam Is a good choice for easy access to dense foam, though Acoustic grade foams are much better as they have a higher hardness and density over standard Open cell PU grades/Visco elastic foam (Memory foam).

Oddly enough, denser furniture foam is also good because the combustion modification process used to make the foam ignition resistant reduces the air flow through the foam. (All UK manufactured furniture uses foam that is Combustion modified).

Foam harness helps (ILD/CLD ratings) but hardness combined with heavy Density gives good sound reduction qualities.

For example standard furniture grades vary between 20-45 kg/m3, packaging foams 16 kg/m3 - 20 kg/m3, whilst high end acoustic foams vary between 50-90 kg/m3. But at the heaviest end you're looking at applications such as insulating a Hercules.

[fangsnatcher]

Re: Sound Reduction.

Knowing chuff all about foam, is the acoustic stuff easy to cut and will it mould into all the nooks and crannies a rifle has. Does it still retain its sound deadening properties when chopped up?

[Figjam]

Re: Sound Reduction.

I've used sorbo in my aeg. Really noticeable difference, combined with a relatively high speed (33 a second) cycle that makes the signature on semi very low, in that the shot is over very fast.
I know a guy who is into air brakes in his sniper cylinder too that is like a mouse fart noise wise.

[fangsnatcher]

Re: Sound Reduction.

Got some dense upholstery foam on another's advice. Spent the grand total of 50p! I'll pack my rifle out and do a before and after with the decibel meter on my phone

[jonny lovegrove]

Re: Sound Reduction.

i need to clear coat my L96, so ill do similar when the sun shows its face next. its 58Db as it is so not very loud at all

[fangsnatcher]

Re: Sound Reduction.

58 is very quiet, are you running a silencer and if so which one and how much?

[jonny lovegrove]

Re: Sound Reduction.

Swiss arms Overbarrel, they went for £40-45 new.

that plus a Laylax silent piston, with sorbo on the cylinder head (standard, as the laylax one made it louder!)
with the PDI airseal hop unit, means theres very little leakage from the cylinder and very little noise from the cylinder itself.

[fangsnatcher]

Re: Sound Reduction.

Well I packed in the foam and have no difference in Db at the muzzle, back to the drawing board. Looks like a silencer is the way to go. Maybe I'll just stay loud!!

[liam88]

Re: Sound Reduction.

The only thing cutting the spring did was make the bolt pull lighter, just tested it on an old spring as my vsr is putting out 70db.... will try anything to make it quieter

[Another]

Re: Sound Reduction.

Packing the body out will reduce the sound emitted around you, but yeah you'll need a silencer to stop the muzzle report and the sound travelling directly forward and away from you.

We could get into foam shaping for acoustic dispersion but that a bit irrelevant in the space sizes in airsoft sniper rifles bodies.

A sneaky fellow I know decided the gun wasn't quite enough with just internal foam for his P90 AEG, and make an external foam jacket covered in ghille to further kill the surrounding noise.

[Trouble]

Re: Sound Reduction.

Really enjoying this thread and the contributions being made