Tag for some "answers".

I rather have a starwars type blaster that whines when I fire it...

no.

I can personally attest to the fact that two subwoofers connected out of phase with each other are hugely quieter than when they are in phase.

I think it would have to be huge to generate enough SPL if you really wanted a Tier 1 Active Noise Cancelling Suppressor.

The terms "firearm silencer” and "firearm muffler”
mean any device for silencing, muffling, or diminishing the report of a
portable firearm, including any combination of parts, designed or
redesigned, and intended for use in assembling or fabricating a firearm
silencer or firearm muffler, and any part intended only for use in such
assembly or fabrication.-US Code chapter-whatever title-whatever section 921

Well, I would be inclined to think that it would be a monster device to deploy.  It would have to be omnidirectional and have some serious power to cancel out the higher dB sound waves of the gunshot.

I don't think that would be something you could build into the size of a standard sound suppressor.

Theoretically possible, but you would need speakers loud enough to generate an equivalent sound (180 out of phase) to the report...



And distribute those waves at the exact same time as the report is generated, traveling in the same directions....



The bose headphones work the way they do, because they are playing right into your ear...



A broadcast version would be much harder to make work...

that wasnt his question..



 

Such systems exist already. They get installed next to noisy machines to muffle the sound. Can't find a link to one quickly though. In the video I saw on this, it muffled the sound a lot, but did not silence it.

Since sound travels out in an expanding sphere, you could probably do it for a segment of it in a given direction, for the shooter for instance.

 

I imagine that a gun shot produces not only a lot of sound but around spread out over a fairly large range of frequencies

I think most suppressors do "noise canceling."
That's only partially a joke. Between cooling, frequency shifting, phase shifting and velocity decrease there's a whole lotta "noise" being canceled.  

I really doubt it. You can suppress it to the point where the human ear cannot detect it, but I don't think you can completely eliminate the sound.

Bose headsets work because they surround the bullet, so I guess if you surround the end of the gun and make the bullet travel through an air tight end fitting, maybe.

Not only that, but for it to work properly the characteristics/timbre of the sound would have to be the exact same, but 180 degrees out of phase.



Sound is colored by its surroundings, and also the location of the observer.
It could be theoretically possible, but pragmatically it could never be done 100%
As an aside, playing with phase cancellation is pretty cool.


If you have a song, and an identical but instrumental version of the song (everything is the same except no vocal track), you can use phase cancellation to extract a vocal track from the original.
 

Don't think it's going to work for the reasons already pointed out that speakers needed to cancel out 150 - 180 dB are going to have to be powerful and likely large.



Remember the sound of a round being fired is due to rapidly expanding gases.  The suppressor works by giving those gases additional volume to expand.

Pretty much.  The sound waves propagate outwards in all directions, and would have to be canceled at every point to be neutralized.  Something that reduces the sound at the shooter could do nothing somewhere else.  I imagine it's doable theoretically, but environmental factors, uneven terrain and propagation media (eg something as minor as humidity) would mess it up royally in the field.



Edit for pun: Suppression alternatives would be truly BAFFLING.  Har har har.





 

you might have better luch with a square shaped 'can' and use modal soundwave cancelation

I remember reading in a gun rag about the Russian an94 having a sonic whistle that was supposed to do just that

This.  Power would be impressive.  Percussive sounds are VERY HARD to replicate.  Take for instance a piano.  If someone is playing one in the neighborhood, it is easily heard through the walls.  But play a recording of it at the same SPL and you would be hard pressed to hear it through walls.
 

It's hard to demonstrate over the internet, but I can provide a visual to help better understand.

Here you can see two sine waves. They are both 440 Hz ("A").
The top represents the left channel, the bottom represents the right.



I inverted the right channel, so the sine waves are now 180 degrees out of phase with one another.
Even in this stereo setup, out of speakers you will still hear a sine wave. It will sound a bit odd in comparison to a normal sine wave, but you will definitely hear it.



As you move your head in relation to the two speakers, the tonal characteristics of the sound will change.
Look to the bottom for an mp3 I just made demonstrating this.
However, if I were to "combine" the two in one channel (i.e. two tracks mono, both 440Hz sine waves out of phase with each other, but played simultaneously), you would hear nothing at all.
Here's the mp3:



The first two seconds is a simple sine wave at 440Hz. Then 0.5 seconds of silence, and then 2 seconds of a 440Hz sine wave with the left channel out of phase with the right.


 

And then...






As the complexities of the tone change (sine waves are as least-complex
as you can get), it will become exponentially more difficult.



The densities and materials used in a rifle will change the sound. The
amount of fouling will change the sound. The construction of the rifle,
etc. Everything will affect the sound in some way.



We may not be able to perceive it now for obvious reasons, but these things would make some difference in phase cancellation.



Further, to do so you'd assumingly have to broadcast the same waveform
as the rifle is producing (but 180 degrees out of phase with one
another), and both sounds would have to hit the observers at the exact same moment (experiment with the latter part of this by moving your head for the 2nd part of the above audio clip).


Recording the gunshot is a HUGE leap, for a great number of reasons.


First, the sound pressure level of a gunshot is enormous. Finding a suitable microphone to handle it is the first step.


Second, microphones hear differently than we do. That ruins it from the get-go.


Placement of the microphone will affect the timbre.


The cables and equipment used will affect the sound.


The speaker, cabinet, and amplifier will affect the sound.


And, remember that sound is the compression and expansion of a medium––it's pressure waves. Differing air densities, etc. will have an effect on the sound.




There are tons more factors that will influence it, too.

Looking at the picture in my previous post, you can see that each
waveform is the exact same wavelength and amplitude, and each crest is
at the same place. For phase cancellation to work perfectly, all of these would have to be the same.

Were you to change any of these (it's impossible not to in this scenario), for instance if the sound from the speaker reached the observer even 100 milliseconds before/after the gunshot, it wouldn't work.

If it was "louder' when it reached the observer, it wouldn't work. If the waveforms didn't match, it wouldn't work.

If it could be done it may be the most practical at first in a sniper type situation.

What about a  continuous purge of CO2 through the can? Would that only affect any flash, or could it impact the noise report as well?

It's already being done the good cans being made today use phase cancellation in order to cancel out the sounds as best as possible. I don't know if I answered your question correctly or I may of misinterpreted it.

LOL, complete and utter nonsense.   Noise cancellation is an adaptive prediction scheme where a digital predictor is calculated in real time and the signal estimate is transmitted in such a way to produce an error as close to zero as possible.   In general since sound waves are spherical, this is done at a single point in space for each predictor.  I can assure you that current cans do not have active noise cancellation technology, with DSPs and speakers.

interesting, i didn't know that.

Thanks, DK.  Now I'm going to have to fill out a Form 1, pay $200, and engrave my name into my newly ATF-registered Boose headphones suppressor.  

And why wouldn't they?  These people have already declared a shoestring to be a machine gun!

_MaH

Doesn't the AN-94 muzzle device do this?

In other words: The Tom Swift novel I read in the 1960's is Never Going to happen out side of fiction.

You'd need an array of REALLY LOUD speakers.

Yeah, you couldn't carry the speaker nor the amp it would take to cancel the gunshot.

Just blast the music loud and put a suppressor on your 9mm pistol and load up subsonic ammo and shoot the target, the neighbors won't have a clue, haha

Theoretically? Yes.....but you are probably looking at a lot of potential complications.

Will your "silencer" be of a size or weight that you will find acceptable?
Will it do anything to detract from the kinetic energy of the bullet?
What will be the power necessary to generate that counter wave?
What kind of computer will be needed to control it if it isn't hard wired into the structural design?

And so forth.

Decades ago, when i was learning about exhaust systems, I conceived of a method to destroy an engine by sending a counter wave through its exhaust pipe that could cause a disruptive condition inside the engine.

My prof's response?

"Yes, it's possible.................................BUT IT WOULD BE AS LOUD AS HELL!" (my emphasis)
_________________________________________________________________
("Can you hear me?"––Oscar Goldman across an auditorium of a cheering audience over Jamie's bionic ear, (w,stte), The Bionic Woman "Bionic Beauty")

No-it retards and re-directs the escaping gas just long enough for a second round to clear the barrel thereby modifying both recoil impulse and barrel rise/line of sight fluctuation thereby (in theory) enabling  two shots to git the same hole.

NO.

Have you ever seen the AN-94 being fired on video?

I would assume that YES, you could make something that would cancel out the sound...


But even suppressed, a firearm can still be pretty loud.  The equipment would definitely not be portable, and probably wouldn't even be very small.  It would take active electronics with a microphone and input circuitry that would not clip the audio, then an amplifier and speakers to play the out-of-phase sound.  

Technically possible, but probably NOWHERE near practical.

I just listened with headphones and my brain imploded. Thanks a lot, asshole!

What software did you use to create that?

I referring to the use of frequency shifting. It's an advanced baffle design that aims to move some of the blast into the ultrasonic range. However, the jury is still out on weather it real works or not.



 

No, but video never picks up gunshots accuratly anyways. Several articles describe the brake as having noise altering properties to protect shooter hearing as well as delaying recoil.

Posted Via AR15.Com Mobile

Damn!  So all I have to do is tape one of these suckers on the end of my deer gun and I'm set???

Im pretty sure there is at least ONE suppressor design that has a rearward "area" with spaces that are designed to use noise cancelling "shapes" to lessen the sound.

IIRC the measurement of the rearward area is very specific as it bounces the sound waves back at half the wavelength as the ones traveling towards it, to help cancel it out.


I WANT to say KAC, but im not sure who, or what company does it... I was reading into it quite a while back.

Yes, we did it as a Mechanical Engineering lab experiment at Virginia Tech back in 1992. It was actually very easy to do.

If a bunch of undergrads could easily do it as a lab experiment, I imagine the black box guys have been using it for decades before in practical applications.

It is very old, very proven technolgy that has been around a very, very long time.