Suppressors Supersonic Crack - How Loud?

[LanceS4803]

Concerning the ballistic/suppersonic crack: What determines how loud it is, velocity or cross section, or both?

For example a .22lr goes supersonic and makes the crack, while a .223 does the same thing. Does the dramatically higher fps of the .223 make a difference in how loud the crack is over the .22lr?
Also, the same .22lr is fired along with a .444 with twice the diameter. Is the .444 twice as loud?

 

[JJones75]

Re: Supersonic Crack - How Loud?

I don't think it's a scale that shows that the bullet diameter is directly related to the noise

shooting a 17 Mach 4 doesn't seem any louder than a 17 HRM when shot though one of my cans and the same goes for shooting my 308 to a 300 win.

But a 17 though a good suppressor is alot quieter than a 50 though a good can

it's more to do with the size of the bullet than the speed , I mean look at the sonic boom from a F-15 as opposed to a 308.

 

[KYpatriot]

Re: Supersonic Crack - How Loud?

JJones is right. On aircraft the size of the aircraft matters, as well as how "sleek" it is. An F15 with bomb racks, targeting pod and FLIR is dirtier and louder than one that is clean.

I would think as far as bullets go that all are clean enough that it would be difficult to discern differences in form factor. I do think you can tell differences in bullet size.

For those that haven't heard it, a bullet going over your head is louder than most people think. To me it seems almost as loud as the report from firing an unsuppressed 22LR. In other words, you cant miss it! Unfortunately (or fortunately, if you are the shooter) , you cant tell the direction it came from without the boom from the muzzle, and in any case the bullet has already passed you before you hear it anyway.

 

[LanceS4803]

Re: Supersonic Crack - How Loud?

Thanks for the info. Acoustical physics is a foreign language to me.

I've worked in target pits before. Someone should warn you about what to expect, as that first shot overhead really gets your attention!

 

[bricktop]

Re: Supersonic Crack - How Loud?

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: LanceS4803</div><div class="ubbcode-body">Thanks for the info. Acoustical physics is a foreign language to me.

I've worked in target pits before. Someone should warn you about what to expect, as that first shot overhead really gets your attention! </div></div>

Yea, it's loud enough that I preferred to error on the side of ear safety and use some electronic muffs, so I could still hear the pit commands.

 

[300WSM]

Re: Supersonic Crack - How Loud?

supersonic 45 a lot louder through can than supersonic 9mm. IMO

 

[Magicman]

Re: Supersonic Crack - How Loud?

Does the bullet crack once when it becomes supersonic and again as it becomes subsonic while slowing down? Is the crack you hear at 100 yd pit the same one as the one the same bullet makes at the 600 yd pit. Since the bullet reaches supersonic before it exits the barrel it seems like the bullet would be making a constant shrieking sound as the air refills the void behind it. Creating a pop or "crack" noise you hear at all ranges. Just askin.

 

[turbo54]

Re: Supersonic Crack - How Loud?

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: 300WSM</div><div class="ubbcode-body">supersonic 45 a lot louder through can than supersonic 9mm. IMO </div></div>

I tend to agree with this.

While I don't think I could pass a "blind" test of which cartridge was which, I've been around suppressed rifles enough to know a 223's crack is nowhere near as loud as the crack off a 338.

 

[turbo54]

Re: Supersonic Crack - How Loud?

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Superdave</div><div class="ubbcode-body">Does the bullet crack once when it becomes supersonic and again as it becomes subsonic while slowing down? Is the crack you hear at 100 yd pit the same one as the one the same bullet makes at the 600 yd pit. Since the bullet reaches supersonic before it exits the barrel it seems like the bullet would be making a constant shrieking sound as the air refills the void behind it. Creating a pop or "crack" noise you hear at all ranges. Just askin. </div></div>

I used to live close to Cape Kennedy, and watched countless shuttle launches and re-entries. There was always a sonic boom both when it went sub-->super, and also when it went super-->sub. I would have expected the same from bullets, but I've never heard it. I've witnessed thousands of bullets hitting the berm, and thus going from 2800fps to zero, and the "crack" of the shockwave just instantly disappears, as far as I can tell.

I've spent a great deal of time in the pits @ 200, 300, 400, 500,600, 800, 900 and 1000 yards, and can say from experience that the supersonic shockwave "crack" that you hear overhead is the same for any given bullet at any given range <span style="font-weight: bold">provided it is well above the sound barrier</span>. A 155gr 308win launched at 2900fps or so sounds a lot more "dull" @ 1000 yards than it does at even 800 yards. I don't understand the physics of this, but know it to be true.

 

[KYpatriot]

Re: Supersonic Crack - How Loud?

With respect to Turbo, a sonic boom is generated continuously while the object is faster than the speed of sound, the shock waves pile up and are dragged behind the object like a wake behind a boat. It is not a singular event that occurs only when it passes through Mach 1, in either direction.

Aircraft are different than bullets in that they turn, and this means that the shockwave can be focused for some observers on the ground. That can make it sound different on the ground. Aircraft, being long objects that generate booms nose and tail, sometimes sound like a quick double boom, but you can't always hear two distinct booms.

The difference in shock for various bullet sizes may not be discernible, but it is there. The more air is displaced, the greater the shock/overpressure. So bigger aircraft (and bullets) should have a bigger and louder shock, all other things being equal. At the same altitude, the Concorde was much louder than any fighter, for instance.

Im not sure how extra speed would affect the strength of the shock. I do know that it doesn't take a lot of over pressure to damage windows. My wingman at Red Flag overflew a manned radar site around M1.2 a couple hundred feet above the ground when we were cheating on an egress. Broke the windows, knocked stuff over, and scared the #$%$ out of the guys there, because it is LOUD, like touching off a fifty right next to you loud. Cost a case of Jack for him, and a carpet dance for me at the mass debrief. Poor radar guys went home.

 

[3DHUSKER]

Re: Supersonic Crack - How Loud?

There will be one audible crack at the point the bullet travels closest to you.

The larger the projectile the louder the crack in my experience.
Also you have to take account the objects around you. Some shots sound louder as there are objects for sound to bounce off and amplify it..

The quietest suppression is experienced in wide open prairies.
Loudest in deep canyons, forested areas or around buildings.

In short super cracks are relative to your surroundings as well as projectile size.

 

[9H_Cracka]

Re: Supersonic Crack - How Loud?

I can tell you first hand a 50 cal at 350 yards sounds like someone popped off a 9mm next to your ear. Way different than a 223 or 308 projectile going by at the same distance.

So much for the theories above.

 

[shadowmaker]

Re: Supersonic Crack - How Loud?

Is anyone aware of published data on the frequency profile of the sonic boom? I would love to see what the waveform looks... especially as a 5.56 or 7.62 round drops out and goes subsonic. My apologies for geeking out on the thread.

Barnes Bullets built a new manufacturing plant & testing facility a few years ago that utilized an electronic paperless target range for gathering ballistic data and test production samples / quality control checks. System measured the coordinates of the bullet passing thru a range mark using measurement of the sonic boom from the bullet. I have no idea who manufactured the system (wished I would have asked). I was too distracted... wishing I too had access to an environmentally controlled 400 yard indoor range

Please PM me (or reply if appropriate) any link suggestion. I don't mean to go off topic and turn this into a triangulation discussion.

Very interesting thread. Thanks everyone!

 

[athhud]

Re: Supersonic Crack - How Loud?

Every action has an equal and opposite reaction. The bullet is displacing a fluid. A bigger bullet displaces more fluid. A faster bullet "ripples" fluid further than a slower bullet. Sound is essentially the rippling of a fluid. I've done no research on the matter, but I'd have to believe that there is a relationship between speed, mass, volume, and sound. Just think of air as water and it's fairly easy to illustrate. Thinking back to High School science class, I'm thinking that mass/volume would correlate with amplitude and speed would correlate with frequency.