PC A silenced 9 mm appears to be louder than a crossbow

[ElCabong]

I wake up more Zed's using a 9 mm with a silencer that I did using a crossbow. I do see the logic of this. Intuitively I would think that a crossbow would be a better stealth weapon than a 9 mm with a silencer.

It's just way more fun to go around caping the Z's. But only slightly more

Is this working as intended?

 

[Fox]

In real life, "silencers" also known better as suppressors, only suppress roughly half the sound of the firearm, meaning they take some of the ear piercing sound away but you can still hear the shot from a good distance. With the larger caliber weapons using suppressors, you still need to wear ear protection because it's still plenty loud.

While I don't know if this game intended for suppressors to work in that manner, I personally have no complaints.

 

[Darthjake]

My suppressed 9mm, works wonders for the occasional vulture in the field, and if I've got a room with 5 or 6 sleepers and only 1 or 2 are radiated, I can use arrows on the normal and then pop both the radiated with not very much noise. Ofc, I'm specced to stealth, and have the armor mods to enhance that too, so that helps as well.

 

[FileMachete]

I think it's working as intended, gameplay wise.

Rl I'd certainly lean towards a crossbow being, overall, quieter, or at least be capable of such.

But there's a 'quality of noise' thing that might make a crossbow "louder/more-likely-to-be-head". Something like the quality of the sound a glass breaking makes versus dropping a large book. They could have the same dB level, or 'sound pressure' but I think most folks would react more to the glass breaking.

If anyone's interested one of the better FAQs I've found on cans/suppressors is by a maker. Clear straight forward answers & explanations with enough details to be useful (they describe the super-sonic crack a bullet may make, and how that fits into the whole thing).

https://www.advanced-armament.com/FAQs_ep_41-1.html

Don't miss questions 11 & 18 for a well rounded understanding of how certain ammunition loads make a large difference.

 

[pApA^LeGBa]

i get why the silencer works that way in game, see the post from Fox. I don´t see the logic with the crossbow beeing so freaking loud in this game.

 

[ZombieSurvivor]

I'm very confused. A crossbow would be more silent than a suppressed weapon in my experience with firearms and crossbows in real life. Whats the issue???

- - - Updated - - -

also the silencer feature was broken, not sure if it ever got fixed.

EDIT: A17.3 Fixed - "Silencer doesn't have much of an effect"

https://7daystodie.com/forums/showthread.php?117027-Alpha-17-3-Experimental-B18-bug-reporting-thread

If you're curious as to how sound is produced with sub-sonic rounds and the cracking sound produce by super-sonic compression of air infront of the round.

This is explained by Dr. Konstantinos Kanistras in the video.

 

[Damocles]

A lot of the noise of a gun is determined by the velocity of the bullet, not just the gas expansion (mussel flash).

Thats why there are sub-sonic versions of the ammunition (bullet slower than the speed of sound) to remove a lot of the noise (breaking the sound barrier).

So the game could have a "sub sonic" mod for guns, next to silencers. (lower damage, lower noise).

 

[FileMachete]

ZombieSurvivor, hey thanks for posting those vid links. Cool to see much better than static images from college text books

First vid also shows why suppressors on revolvers are doomed to failure, heh (gap between cylinder & barrel lets out the boom).

Damocles, you're right, but maybe only half . Adding in sub-sonic ammunition would lower sound output, assuming the 'normal' round was super-sonic. Which basically covers what's in-game so far (no idea on A18).

But 'slower', doesn't necessarily mean lower damage. F=ma so in some cases loss of speed can be offset by more mass.

And the 9mm round is a perfect example of that.

The 'normal' 9mm round is just barely supersonic. In standard pressure rounds (not the +Ps) upping the bullet weight results in the round falling below ~1100 fps, yet maintaining or even slightly increasing muzzle energy (depends on maker/load/etc).

Obviously the 7.62 (.30 caliber) rifle ammo the game mimics would be expected to much faster. Typical 'normal' 7.62x51 military ball ammo clocks in around 2750 fps. And trying to offset more than ~60% of it's velocity with mass won't work due to size constraints, so a sub-sonic 7.62x51 round has a lot less energy than it's 'normal' brother. Say very roughly 420 ft-lbs vs 2800 ft-lbs

Interesting to note that the .30 caliber "300 AAC Blackout" that they used in vid can reach around 550 ft-lbs of energy with sub-sonic loads, even though it uses the much smaller .22 caliber 5.56x45 case necked out to use a .30 cal bullet.

Reason is the 300AAC can use much heavier bullets, but they have to be stabilized by faster twist rifling than the .308 Win (civilian equiv of the 7.62x51 NATO), since the 300AAC doesn't have to support the much higher velocities the .308 Win reaches (300 AAC tops out around ~1600 fps).

Sry to be pedantic on this. I know it can be confusing, but always hearing, "there's a silencer on it. so it's less powerful." gets old :-/

Putting a can onto a firearm will almost always -increase- velocity a wee bit, meaning a bit more energy. Not enough to matter, but certainly not an automatic decrease (using the same ammo of course).

 

[warmer]

Remember bullets make A LOT of noise when they hit things. It might be quieter going out of the barrel, but the sound of it impacting anything doesn't change a bit.

 

[Fox]

Remember bullets make A LOT of noise when they hit things. It might be quieter going out of the barrel, but the sound of it impacting anything doesn't change a bit.

If a bullet hits dirt, than it just sounds like someone throwing a rock at dirt... not much difference. If a bullet hits a drum or steel plate, then ya, you can hear that "ting!" sound from a mile away, but likely still sound like someone threw a rock at it. Explosive rounds on the other hand... might add more sound.

Also, Mythbusters proved that even a .50 BMG round passing between 2 very thin panes of glass does nothing to the glass because the shockwave is extremely weak. If the shockwave is that weak, I'd say it's likely not creating that much sound other than maybe a "whizzing" sound as it flies passed you. Almost all of the sound you hear from firearms is from the explosion of the gunpowder and a bit from the firearm reaction (bolt / slide knocking back, that sort of thing).

 

[warmer]

If a bullet hits dirt, than it just sounds like someone throwing a rock at dirt... not much difference. If a bullet hits a drum or steel plate, then ya, you can hear that "ting!" sound from a mile away, but likely still sound like someone threw a rock at it. Explosive rounds on the other hand... might add more sound

Agreed. I guess part of my point was, if you are near the intended target, you are going to get alerted. Given that headshots are how most people roll, I just imagined the sound of heads exploding as my baseline instead of dirt, but I definitely see your point.

 

[Damocles]

If a bullet hits dirt, than it just sounds like someone throwing a rock at dirt... not much difference. If a bullet hits a drum or steel plate, then ya, you can hear that "ting!" sound from a mile away, but likely still sound like someone threw a rock at it. Explosive rounds on the other hand... might add more sound.
Also, Mythbusters proved that even a .50 BMG round passing between 2 very thin panes of glass does nothing to the glass because the shockwave is extremely weak. If the shockwave is that weak, I'd say it's likely not creating that much sound other than maybe a "whizzing" sound as it flies passed you. Almost all of the sound you hear from firearms is from the explosion of the gunpowder and a bit from the firearm reaction (bolt / slide knocking back, that sort of thing).

Supersonic bullets make a lot of noise just by them breaking the sound barrier, not just a whizz.

Thats why "silenced" guns will use sub-sonic ammunition.

https://en.wikipedia.org/wiki/Subsonic_ammunition

 

[Fox]

I don't know... maybe I'm wrong... but it's so hard to tell if the sound demonstrated in the video is from the gunpowder explosion or if it's just the bullet whizzing by. Too bad it wasn't recorded in like 2000fps or something with an oscilloscope to prove 2 separate sounds.

Thinking about the whip from Raiders of the Lost Ark... while not too ear piercingly loud, it's still impressive for a tiny piece of leather. But I'm also thinking about how long does the bullet stay past the barrier... cuz most bullets are only set for a bit past the sound barrier.

 

[ZombieSurvivor]

You should watch the two vids i posted, would give you a much better understanding of the science behind all this.

Not sure how those guys have 7m subs lol. based on that one video they really do not know how to set up recording equipment lol.

I still do not understand what sound they were trying to capture using that horrible set up.

 

[Damocles]

You can hear two sounds when the bullet passes. The first high pitch is the (supersonic) bullet, sounding like a whip, the second (delayed) is the muzzle gas-expansion.

That "whip" sound, is what gets suppressed with sub sonic ammunition.

An AK47 has a muzzle velocity of 2,350 ft/s whereas the speed of sound is 1,125 ft/s. So its more than twice as fast. (but will slow down of course)

If you suppress the muzzle, the bullet can be still heard loudly, but not the direction where is came from. Its way harder to pinpoint the position of the shooter from the muzzle sound.

 

[ZombieSurvivor]

You can hear two sounds when the bullet passes. The first high pitch is the (supersonic) bullet, sounding like a whip, the second (delayed) is the muzzle gas-expansion.
That "whip" sound, is what gets suppressed with sub sonic ammunition.

An AK47 has a muzzle velocity of 2,350 ft/s whereas the speed of sound is 1,125 ft/s. So its more than twice as fast. (but will slow down of course)

If you suppress the muzzle, the bullet can be still heard loudly, but not the direction where is came from. Its way harder to pinpoint the position of the shooter from the muzzle sound.

You know your stuff, nice. I would add though, a bullet can be fired slower than the speed of sound and still produce a sonic boom i guess you call it. This is caused by the compression of the air infront of the bullet and the air being compressed having to flow around the bullet can be faster than sound thus causing and sonic boom. gotta love science.

Note: I'm probably explaining this incorrectly lol, i do not feel like looking this up in detail.

 

[FileMachete]

<snip>


But I'm also thinking about how long does the bullet stay past the barrier... cuz most bullets are only set for a bit past the sound barrier.

 


Happened to notice on the wikipedia page for 7.62x51 that one of the loads stayed supersonic out past 1100 yards. Most reloading tables don't go past ~5-600 yards for rifles, so can be hard to find where a given round drops down.

 


On the second bit... hmm. History wise that's pretty true. Black powder burns faster than modern smokeless does, so in a sense, chamber pressure was a bigger deal. Also non-cladded bullets (exposed lead) limited speeds. Much past ~1350 fps and there'd be a lot of lead left coating the bore.

 


More modern stuff it's mainly the 'pistol' rounds that stay under say ~1400 fps. While I can't think of a modern rifle round that would be under a couple thousand feet per second (at the muzzle) off the top of my head, one bunch that might well be there would be some of the newer 'large mammal brush gun' rounds. Large caliber, very heavy bullet rounds designed for use hunting bear or moose. Basically modern day cousins of the classic Nitro Express african rounds.

 

<snip>


If you suppress the muzzle, the bullet can be still heard loudly, but not the direction where is came from. Its way harder to pinpoint the position of the shooter from the muzzle sound.

 


Absolutely. And one of the main reasons 'snipers' use suppressors even with full power, supersonic loads. Other being that cans greatly reduce the muzzle flash (and dirt plume from the gases).

 


On the supersonic 'crack'. I can't quote the physics/math but there's a definate correlation between how loud the crack sound is and the speed of the bullet. There's a noticible difference between a .22 LR moving at ~1300 fps vs. a 5.56x45 (which is also a .22 caliber bullet) moving at over 3000 fps.

 

[ZombieSurvivor]

<snip>On the supersonic 'crack'. I can't quote the physics/math but there's a definate correlation between how loud the crack sound is and the speed of the bullet. There's a noticible difference between a .22 LR moving at ~1300 fps vs. a 5.56x45 (which is also a .22 caliber bullet) moving at over 3000 fps.

The first video i posted goes in depth the science behind it if you are curious to know why and how this happens. I suck at explaining things in text, talking ov video on the other hand very easy, best just to watch the vid lol

 

[FileMachete]

The first video i posted goes in depth the science behind it if you are curious to know why and how this happens. I suck at explaining things in text, talking ov video on the other hand very easy, best just to watch the vid lol

hmm, I watched them both... First one went into how the angle of the wave front could be used to calaculate the Mach number, which is very cool, but I don't recall them talking about the energy levels or how they related to the sound pressure?

I mean, no question it makes sense that the larger and faster an object is that breaks the sound barrier, the louder the sonic boom will be, I just can't point a finger at an equation that would show the .22 LR's boom as X dB and the 5.56 as x% more.

 

[ZombieSurvivor]

I mean, no question it makes sense that the larger and faster an object is that breaks the sound barrier, the louder the sonic boom will be, I just can't point a finger at an equation that would show the .22 LR's boom as X dB and the 5.56 as x% more.

Oh my bad I misunderstood your statement, I re-read it. Yeah nevermind those videos do not address any of that. Now I am curious and I'll look in to it because now I want to know. If I find an answer I'll post an update.

EDIT #1: Interesting article, does not answer what we are talking about but interesting none the less. http://firearmsid.com/Feature%20Articles/soundofbullets/soundofbullets2.htm