How do they do that?

[Dan Robinson]

I know HPA wankers have their super quiet sneaky peaky pews that make that disturbingly quiet little thumping noise when the trigger is pulled.

But what about the AEGs I see doing that.....  how is that achieved?

Is it shimming?

A fancy Schmancy brushless motor?

Gears make from Adamantium and powdered kitten paw pads?

 

[Krisz]

I know HPA wankers have their super quiet sneaky peaky pews that make that disturbingly quiet little thumping noise when the trigger is pulled.

But what about the AEGs I see doing that.....  how is that achieved?

Is it shimming?

A fancy Schmancy brushless motor?

Gears make from Adamantium and powdered kitten paw pads?

HPA is only "quiet" when you put an HPA engine into a gun and attach a foamed suppressor to it. Otherwise a slide on a pistol or a bolt on a gbbr still makes a very distinguishable noise regardless running them on HPA. To be honest even HPA engine can be heard up close (let's say you're within 5 meters) and every engine has its own noise signature. A kythera sounds different compared to a jack or inferno etc.

I don't think that an AEG can be as quiet as an HPA because those moving gears always make a noise regardless what you do. Altough some peple put foam into certain guns to make it happen (I only read about AUG and P90's because there is a lot of empty space in both guns for insulation).

But answering your question yes shimming your gears to death to achieve that deep, thumping noise is supposed to be the ultimate solution. Plus adjusting motor height. 

 

[Sewdhull]

Ppl will get the gearbox as quiet as they can.

Gears whirr and don't always mesh properly regardless of shimming  but it's a worthy task.

Reduce the piston noise with pads or even an airbrake, match the spring and volume to reduce the slap and the muzzle report. Pad the reciever with butyl soundproofing.

Silencers do reduce the muzzle report and slap noise getting out but it's a lot of work it seems.

Absorbing the higher frequencies does a lot for changing the perception of the loudness and the ability of the ear to percieve direction.

 

[Fatboy40]

# match the spring and volume to reduce the slap.

# Silencers do reduce the muzzle report and slap noise getting out but it's a lot of work it seems.

# Absorbing the higher frequencies does a lot for changing the perception of the loudness and the ability of the ear to percieve direction.

It's the above that I've found with my playing around with mechanicals as well.

For the first point I now run a full cylinder in my v2 DMR with an M120 spring, I swapped to one around a month ago from a 4/5 and M130, and the increased air volume has 100% increased noise (just look at a G&G Firehawk to see this in action). If you're not shooting heavy BB's, and have a very good air seal with a 3/4 cylinder, an M95 spring can make a huge difference to noise.

For me the biggest thing that helped my AEG on points two and three were a foam suppressor, changed the "twang" to more of a "thump", and swapping from a spring on my inner barrel to o-rings. Do what you can to try and change how the rifle "resonates", and I've found that polymer rather than metal receivers also help.

 

[Sewdhull]

Whilst I've not gone into this too much, there's air pressure making a soundwave and the sound from the slap of the piston travelling out the barrel that can be dealt with by a silencer.

Baffles help with noise and foam will absorb some of that sound.

Baffles bend the sound away from the BB path allowing it to be absorbed.

One day I'll measure the sound empirically, but baffles seem to work well.

 

[Leo Greer]

First off, AEGs and HPA both use the same general system (pressurized gas) to power the BB. You get a muzzle noise when there is too much gas being used for a particular BB weight and barrel length, regardless of system used. One of the easiest ways to quiet your replica is to properly volume it. Second, really good shimming helps a lot (some gears are louder than others but shimming usually helps). I don't aim to make my replicas as quiet as possible (no augs filled with dynamat), but on most of my replicas you can hear nothing but the piston head hitting the cylinder head. I don't use buffers on my Arcturus replicas (they have perfect AOE already), but I'll see if I can link a video to show what I'm talking about.

If you want to really know how to get an AEG as quiet as possible, go to AirsoftSniperForum and check out 1Tonne's thread, but in summary, HPA doesn't have to deal with any kind of gearbox noise, most of which is produced by the bevel to pinion gear junction, and the piston hitting the cylinder head.

 

[Dan Robinson]

Interesting reading chaps.  I'm surprised (but thinking about it shouldn't be) that a suppressor can make a significant difference.

But then I suppose I have my head close to the gearbox of my pews compared to a few feet away when lamenting the apparent silence of other's; so there's a certain amount of misconception I suppose.

 

[Tommikka]

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But then I suppose I have my head close to the gearbox of my pews compared to a few feet away when lamenting the apparent silence of other's; so there's a certain amount of misconception I suppose.

You’ve smashed that hammer right onto its head

We hear what is nearest to us and that which is further away is relatively quieter than it would be up close

We don’t fire with explosive elements, so we don’t get the bang, which means our noise is down to the moving parts plus the escaping air/gas - no matter whether the air/gas came out of a pressure vessel or compressed in a tiny chamber as we fire 

Some body’s may muffle or amplify the mechanical noise - but that can also dissipate in our own proximity 

The escaping air frequency is nowhere near as powerful as in real steel and doesn’t have enough power to disapear into a real steel suppressors baffles.

Over engineering of supressor baffling in our toys might have no effect, but then right one with the right barrel can have an effect 

I’ve made my own with sponges, scouters etc with varying effect and also had some made for me 

But the most effective one I have is a carbon fibre tube, just the right size to slip onto a ported barrel and it somehow absorbs the pop of the barrel - it probably only takes away vibration in the barrel, but it might also be absorbing vibration from the minuscule amount of air trying to escape through the small are of each port

It could also of course just be a well made barrel 

It does have a high level of psychological effect 

 

[Egon_247]

Take my AUG for example....

Head is RIGHT NEXT to the damn gearbox when youre using it. Original TM gearbox was the typical AEG noise box and wasn't great.

Shimmed it properly, new gears (after the sector ate itself with the addition of a new spring ) and a decent splodge of grease (i use CV joint grease on my gears). Sounded ok. 

So then i went mad and added some dynamat inside (have to say, not the nicest of jobs but it works!) and then a Warhead motor.

The barrel stops short of the end of the "suppressor" so it dissipates some of the pop of the tightbore.

Its quiet. Not HPAw quiet, but enough to get comments on it. 

Now if i could just get it to fire in semi, instead of just auto, life would be awesome....  ?

 

[Sewdhull]

Yeah a thin rigid plastic or metal body will transmit that sound quite well and with your ear next to it will seem loud. Butyl will reduce this alot, esp to anyone distant.

The barrel report which is directional potentially can be heard at greater distances if it is loud, but as we know some guns are quiet without any silencing.

I think getting the voluming right is probably the most effective silencing, but if for whatever reason you want to reduce that report somewhere contained for the air to expand into will reduce that pop.