The Hush Hole?

[Hush]

What the hell is a Hush hole you may ask, have you been drinking Hush? Nope, I have not, let me explain.
As many here know I'm an old codger, 74 to be exact and I've been interested in cans since my pre-teen years and discovered what I call the Hush hole at the age of around 12 or 13 y.o. which was many years back and there is no evidence to prosecute me and this is not an admission of guilt as after all these years it might just have been a dream.
Well I'm sure you all have heard or read about noise cancellation, a neg. noise pulse canceling out a positive noise pulse which I have found works for a .22 lr can anyway.
Here is what I did, I made a simple flat baffle can for my .22 rifle it worked pretty good as it was slightly over-sized for the caliber and was nice and quiet but I still wasn't happy, there has to be a better way and I must have read something somewhere about noise cancellation as I decided to give it try, I drilled a small hole about in the center length of the tube, wow, louder as you would expect, so naturally I had to plug that hole, the only thing I had in the proper diameter to plug it was a copper capillary tube from a refrigerator and it had a center hole running through it about .010 in size so I carefully cut off about a quarter inch length and plugged the hole in the can and took another shot to see if I corrected the problem and found to my amazement it nulled the report completely, I decided that the hole in the can at a certain point along its length with a certain diameter opening lets out a certain amount of gas to be looked at as a positive pulse peak being closer to the muzzle of the rifle barrel and any gas or sound pulse coming from the muzzle of the can a negative pulse and canceled each other out.
I write this now as I'm coming to the end of my days and I'd like to see someone carry on experiments along this line.
I gave this info to another member who lives in another country to try and he found it interesting so I want to encourage people to experiment further, perhaps a quieter 9mm can is waiting out there for someone to discover.

[TOOL1075]

phase canceling, huh. sell it to Bose.

pics? I like the idea, but it seems incredibly ammo and host sensitive, among other things...

[LavaRed]

I have been thinking more about it and experimenting, to be honest (Having a .22 silencer that can be taken apart in sections lets me play with a lot of things), and I have come up with a hypothesis:

1) The sound pulse from a well-designed suppressor should mainly resonate at a frequency determined greatly by the suppressor itself, like a wind instrument of sorts.

2) A hole situated halfway along this length will, apparently, produce a soundwave out of phase with the main pulse by half a wavelength. This would appear to indicate that the suppressor's resonating wavelength is related directly to its length.

3) Therefore, all that would need to be done is to calculate the diameter of Hush Hole which releases an equal amount of pressure to that released at the silencer muzzle, which would, theoretically, produce total noise cancellation, as far as the suppressor is concerned. There will still be some sounds, mainly the primer noise, firing pin noise, action noise in smi-autos, et. all.

Other than having a silencer that takes apart in sections, and spare, hollow sections to experiment with different hole sizes, I have realized there is another way to experiment with different hole sizes, which does not require having spare silencer parts:

You buy several aluminium allen stud screws, the small ones without a head, and then hole and thread your tube so that the screws will thread into the hole. Then, you hole each of these with a different diameter hole down the center, and you're done. Now you can experiment with different size hush-holes until you have found the optimal one.

But I will attest to the effectiveness of the Hush Hole, having tried it in my Beretta 70. It is now barely as loud as dropping a phonebook on a hard floor, indoors, which is, in my opinion, Hollywood-quiet.

[LavaRed]

phase canceling, huh. sell it to Bose.

pics? I like the idea, but it seems incredibly ammo and host sensitive, among other things...

I'll post pics later and maybe a video or two, indoors.

[Hush]

Brilliant, I like that idea

You buy several aluminium allen stud screws, the small ones without a head, and then hole and thread your tube so that the screws will thread into the hole. Then, you hole each of these with a different diameter hole down the center, and you're done. Now you can experiment with different size hush-holes until you have found the optimal one.

Less waste, use wire size drill bits, great idea.

[LavaRed]

Video as promised.

http://s137.photobucket.com/albums/q220 ... I_1088.mp4

I was shooting indoors, target was 7 feet distant, phonebook with 3/8" steel plate as a backstop. As you can hear, most of the audible noise, aside from mechanical noise, is the bullets hitting the steel plate after having penetrated the phonebook.

I would say this qualifies as extreme silence.

[Hush]

I loved the video, my contribution to the silencer world.
I liked seeing the effect of the gases coming out the front and side, it kind of shows whats happening, I'd really like to see a shadowgraph of the sound waves interacting, that would be cool.
Thanks for the video Lava Red.

[bikefreek]

woudnt the amount of cancelation depend on your relation to the muzzle? the high pressure wave would be canceled to the shooter but not to someone beside or in front of the gun since the pressure waves are no longer timed properly.

[LavaRed]

I loved the video, my contribution to the silencer world.
I liked seeing the effect of the gases coming out the front and side, it kind of shows whats happening, I'd really like to see a shadowgraph of the sound waves interacting, that would be cool.
Thanks for the video Lava Red.

And a very significant contribution it is, I daresay. I am thoroughly indebted to you for having shared this with me, and I hope to be able to carry it further, seeing as I have a suppressor that allows me to experiment and tweak. I've also been in touch with some of my mathematician and physicist friends, and on showing them the principle, put it to them to develop the equations that model this problem, so that the optimal sized hole may be discovered, and the principles understood.

Yes, it would seem logical that one's position relative to the suppressor would affect the amount of cancellation. There is no doubt that there is a significant cancellation in all directions; I have had people listen to it at various distances and different directions, and they all report a much improved sound reduction. I suppose several microphones in different directions would be required to accurately determine the effect of the hole's position on reduction. However, I don't have the means to test that, for now.

[Hush]

Having given it a little thought I don't see why a capillary tube with the proper size inner diameter cannot be tapped into the Hush hole and run along the silencer body ending at the front of the silencer muzzle having the gases escape closer together for better cancellation although who knows, in doing so it may have an effect on the frequencies involved, this is why I feel further experimentation is needed, especially in larger pistol calibers.

Hush

[TOOL1075]

multi-chamber silencers with multiple gas exit holes? now you're talking. continue to brainstorm, I like it.

after you come up with something that looks like it came out of the Matrix (the part where you see the people in the pods with all the tubes connected to their bodies.... give me a break, it was on TV yesterday) post a concept-sketch

no, but in all seriousness.... your conceptual ideas about wave attenuation and cancellation are fun - but practicality will be your limit in this problem. Geometry of the observer's position, the shooter's position, the ammo type, the host type; these are just a few things that will play a role in whether or not this would be worth while.

you need some good microphones, some good measurement equipment, an audio engineer, and an exceptional grasp of the concepts in the first link of a haphazard google search:

http://cnyack.homestead.com/files/afourtr/invfoutr.htm

I bet you can come up with some pleasing results to the ear - at the shooters position, in common shooting positions. And I bet you could come up with tactical hole plugs for situations involving various room sizes and geometries. Maybe.

"tactical hole plugs" - that's what she said.

[Hush]

no, but in all seriousness.... your conceptual ideas about wave attenuation and cancellation are fun - but practicality will be your limit in this problem. Geometry of the observer's position, the shooter's position, the ammo type, the host type; these are just a few things that will play a role in whether or not this would be worth while.

Possibly true but to what extent? This is where experimentation comes into play, which for someone like me would consider it fun, it works on a .22 and I'd like for someone to try it with a 9mm, but all in good time, Rome wasn't built in a day, lets see what Lava Red and his friends come up with in their findings.
If its quiet in a room with four walls to reflect any sound to the shooter Lava didn't notice it and that's a positive in my book, it can only be quieter outdoors and I'm willing to sit and wait for their findings, heck, I've been sitting on this all these years I can wait a bit more (that is if it wasn't a dream )

[LavaRed]

no, but in all seriousness.... your conceptual ideas about wave attenuation and cancellation are fun - but practicality will be your limit in this problem. Geometry of the observer's position, the shooter's position, the ammo type, the host type; these are just a few things that will play a role in whether or not this would be worth while.

Possibly true but to what extent? This is where experimentation comes into play, which for someone like me would consider it fun, it works on a .22 and I'd like for someone to try it with a 9mm, but all in good time, Rome wasn't built in a day, lets see what Lava Red and his friends come up with in their findings.
If its quiet in a room with four walls to reflect any sound to the shooter Lava didn't notice it and that's a positive in my book, it can only be quieter outdoors and I'm willing to sit and wait for their findings, heck, I've been sitting on this all these years I can wait a bit more (that is if it wasn't a dream )

My mom was in the room behind me, and she said it was exceptionally quiet. As you've probably realized by now, she helps me in the experiments a lot.
I don't have subsonic 9mm or a suppressor for it tho, so most likely it will be done on a .45, when my new .45 can is finished. I will try redirecting gasses forward with a specialized capillary tube too.
And I'll try getting a real job to finance construction of a sound-chamber with microphones and all.

[bikefreek]

what are the odds the little holes are actually just bleeding off pressure and slightly increasing turbulance? A small hole leaking gas should produce sound fairly high in frequency, maybe alot of that sound is above the range for humans or just below the sound levels produced by the gun... so if the holes bleed off pressure from in the can then thats less that is coming out of the big hole in the front, making it quieter.

[Hush]

what are the odds the little holes are actually just bleeding off pressure and slightly increasing turbulance? A small hole leaking gas should produce sound fairly high in frequency, maybe alot of that sound is above the range for humans or just below the sound levels produced by the gun... so if the holes bleed off pressure from in the can then thats less that is coming out of the big hole in the front, making it quieter.

That's an interesting theory which I believe a frequency analyzer would verify, keep the thoughts and ideas coming, this is fun.

[SRM]

Seems to me that a tube from each chamber could be run out to the endcap.

A mono-core might be easier. At the endcap, have removeable orifices with different hole sizes.

One could then play with which chamber did what .

With everything coming out the same end, I think it would work better.The orifices might have an angle to them so they jet across the main aperture. Just a thought.

[Hush]

Seems to me that a tube from each chamber could be run out to the endcap.

A mono-core might be easier. At the endcap, have removeable orifices with different hole sizes.

One could then play with which chamber did what .

With everything coming out the same end, I think it would work better.The orifices might have an angle to them so they jet across the main aperture. Just a thought.

Well its something to consider as they go along.

[winsor]

what are the odds the little holes are actually just bleeding off pressure and slightly increasing turbulance? A small hole leaking gas should produce sound fairly high in frequency, maybe alot of that sound is above the range for humans or just below the sound levels produced by the gun... so if the holes bleed off pressure from in the can then thats less that is coming out of the big hole in the front, making it quieter.

This makes sense. IMHO, pressure release make it quiet not a frequency cancellation.
I used to think of this 'relieving hole' but did not give a try.
Interesting to try on the 9.
What size of a 'hush hole' should I start with?
Anyone has any idea?

[mikes2103]

****carb jets***** tap to the right size and you have a limitless supply of cheap, different size orifices. any drag racer in town is bound to have piles of old jets.

[Hush]

****carb jets***** tap to the right size and you have a limitless supply of cheap, different size orifices. any drag racer in town is bound to have piles of old jets.

Try .010 or smaller to start.

[LavaRed]

Pardon my ignorance, what's a carb jet?

[Hush]

Pardon my ignorance, what's a carb jet?

He had me scratching my head over the carb jet also so I looked it up, its part of a carburetor, see here: http://www.cartpartsplus.com/performanc ... -jets.html

I was never into rebuilding carburetors or working on cars.

[Downrange]

This is really cool, thanks for posting.

There might be a whiz kid somewhere who could create/adapt software for modeling the effects that play into this - wouldn't that be cool?

[Hush]

what are the odds the little holes are actually just bleeding off pressure and slightly increasing turbulance? A small hole leaking gas should produce sound fairly high in frequency, maybe alot of that sound is above the range for humans or just below the sound levels produced by the gun... so if the holes bleed off pressure from in the can then thats less that is coming out of the big hole in the front, making it quieter.

This makes sense. IMHO, pressure release make it quiet not a frequency cancellation.
I used to think of this 'relieving hole' but did not give a try.
Interesting to try on the 9.
What size of a 'hush hole' should I start with?
Anyone has any idea?

Like I said in a few posts back try .010 or smaller to start with.

I'd like to see someone run one through a sound meter someday to see the actual db reduction along with a shadowgraph to show the cancellation effects if that's what's happening which I believe is.

[LavaRed]

This is really cool, thanks for posting.

There might be a whiz kid somewhere who could create/adapt software for modeling the effects that play into this - wouldn't that be cool?

I'll have my computer-savvy best mate look into it.