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Home Defense 9mm vs. 45acp Noise Factor?

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66K views 118 replies 67 participants last post by  Instymp  
#1 ·
I have several handguns, and I'm currently trying to decide which one to use for a home defense/bump in the night gun. I know there are several issues involved in that, and I don't want to get into the whole 9mm vs. 45 debate, but I do have a question regarding these two calibers. My specific question involves the noise that would be involved if I ever had to discharge my weapon inside my home. There's no way that my wife, daughter, or I would have time to put on hearing protection beforehand. So, given that consideration, which would likely cause the least ear damage to me and my family if fired indoors -- 9mm or 45? Or, is there some other caliber that I should be considering?

I've done a lot of reading about this on the internet, but wanted to tap into the wealth of experience available here on DC. Thanks in advance!
 
#2 ·
It's a good question, but IMO it's not going to matter much, they could both cause some hearing damage. There are too many variables involved to determine which could be worse. This topic makes a strong case for suppressor use on a home defense gun.
 
#13 ·
Decibel scale is exponential.

9mm comes in at 159.8 dB and 45 acp at 157 dB for a difference of 2.9 dB.

Well every 3 dB is a factor of 2 in sound energy, so there really is a difference and 9mm is significantly louder.

But, this probably assumes some choice of ammo and different ammo would have different noise generation.

Also, a long barrel gun probably generates less noise than a short barrel.

So in practice, it may not matter that much.

Can't have something for nothing.

Also, how much difference does a factor of 2 make in ear damage?

According to that table, 45 Colt should be a good choice. Even with low power (and low noise) cowboy loads, those big bullets would be effective.

Outside of 22lr, the 32 long is the quietest handgun round in the table. But to be an effective defense caliber, you would need to use something like Buffalobore's hot 32 long loads and they may be louder that whatever the guy making the table tested.
 
#4 ·
you could break down the math. a barrel with hot expanding gasses pushes out a bullet is technically a pressure vessel. given the same barrel length a .45 will have slightly greater internal volume. the 9mm usually operates at a slightly higher pressure between comparable loadings. When that pressure vents to atmosphere is when you get your over-pressure wave we describe here as "noise". generally the level of pressure contained in the vessel determines how noisy it is when is vents. that's why diesel engines are loud.

but a handgun barrel is so small, and at such high pressure, and the difference between 9mm and .45 so small when looked at on overall %, I think Mike's above "not much noticeable difference" is the correct answer.

...or read his linked article, or do the math.
 
#40 ·
... the difference between 9mm and .45 [is] so small when looked at on overall %, ... "not much noticeable difference" is the correct answer.
I'm with SCfromNY: Probably depends on ammo. Supersonic 9 mil ammo will probably produce a crack, just like a .357MAG, whereas the .45ACP is sub-sonic so it will probably produce less. Select ammo that has less than 1,127 ft/s and you shouldn't get "the crack" of the sound barrier being broken. Which will probably mean going with the heavier 147gr bullets in standard pressure cartridges. Gold Dot 147gr 9 mil goes about 985 fps. That should be pretty close to 230gr .45ACP.
 
#7 ·
Any non-suppressed firearm is going to have the potential to damage hearing when fired without hearing protection.

I would use other criteria to make your choice, and if you are really concerned about it, look into suppressors.
 
#8 ·
Back in the old days when we did not use eye and ear protection, I got to shoot indoors in a typical bedroom setup to train for home defense. When I shot the .45 ACP it was so loud that it startled me and I almost pulled the trigger again. My ears were ringing until the next morning. With my 9mm, a few months later, it was not bad at all. No ear ringing, no startling or disorienting effect. Less penetration too. I had shot a 1911 in combat and thought I was used to it, but indoors it is something else. So many people watch movies when everyone is shooting indoors and no one has a problem with it. In real life it is very different and you can easily lose your hearing temporarily and not be able to hear someone approaching you or where other shots are coming from.

For this reason, I have a Glock 19 with laser in my night table. Less noise and less interior penetration. I was in the Mobile Artillery and then the Mechanized Calvary (Tanks instead of horses). No one issued ear plugs in NAM and I stood next to and slept near 175mm/155mm guns firing all night. The .45 in that room was worse than anything else I had heard.
 
#9 ·
Interesting, that by Mike's dB chart, the 9mm is almost 5 dB louder than the .45. Remember, that decibels are logarithmic, so that is close to quadruple the ear damage. Yikes.

(Edit: Oops, misread the .45 Colt levels as the .45 ACP)
 
#10 ·
Interesting, that by Mike's dB chart, the 9mm is almost 5 dB louder than the .45. Remember, that decibels are logarithmic, so that is close to quadruple the ear damage. Yikes.
I was told there would be no word problems.
 
#28 ·
Mike's chart seems accurate. A 9mm operates at nearly double the chamber pressure of a .45 ACP, so it makes sense the sound pressure would be about double.

But, that might not be the whole story. A .45 is pressurizing a substantially larger volume of gas, so that may make the effect on a nearby ear worse than the pressure number indicates. Sounds like a question for a doctor?

As to penetration, either a 9mm or a .45 will go through multiple interior walls, as will most any projectile that will reliably go through a human being. If it's a major concern, you can go with frangible (fragmenting) ammo of various types, but they generally don't have a good reputation for stopping power.
 
#29 ·
Having fired many different handguns indoors with no protection, they all will cause damage. How much is variable on the room fired in, high pressure or low, and other esoteric things. If you only have to do it once in your life the damage is negligible. Its the prolonged exposure to repeated loud noises that does the damage. Any vet who saw combat (with no protection) has had some lose. I came home from 'Nam with 65% gone in one ear and 50% in the other. I have no clear idea how much more is gone due to frequent firearm usage and ageing. No matter what round you fire in your house it will sound LOUD, but you will likely be so amped up you wont notice it until later. The 45acp will be less likely to over penetrate, with good hollow points, than the 9mm with HP's.
 
#30 ·
Putting hearing protection on while investigating a bump in the night has its own potential set of consequences unless the BG is also wearing hearing inhibitors.
 
#31 ·
I think the main difference is the louder "crack" on 9mm. If my early education is remembered correctly the speed of sound is 1100 ft per second and if that speed is broken you get a loud sound. If your 9mm's ammo and barrel length contribute to a speed faster than sound the crack will be IMO significantly louder than a .45ACP. So a compact size 9mm with 147 grain cartridges will be softer sounding than a 115 grain out of a 5" barrel. That is my thought anyway.
 
#32 ·
OK, I've shot a ridiculous number of rounds without hearing protection. Nobody talked hearing protection when I was in college and shooting everything that moved (or not) without protection. I suffer from hearing loss but I function fine in society with a few more "WHAT?? " questions than other folks but if in the RARE eventuality you actually need to shoot a few rounds in your house - you are not suddenly going deaf.

Don't make this a bigger deal than necessary. Yes, Your ears may ring for a few days. Once after shooting a couple hundred rounds through my Walther P-38 my ears rang for a month. But a couple rounds in the house? Sorry, not that big a deal. Especially compared to what happens if you don't shoot.

As to over penetration, that is one of the reasons I have a shotgun with #4 waiting for the bad guy to enter the hallway to my bedroom.I'm still getting the threaded barrel and suppressor for my handgun but the shotgun will be my primary "goto".
 
#35 ·
Be it a 9mm, .45 ACP, or whatever, you will sustain damage. Hearing damage is cumulative. The ear doesn't "heal" and undo damage.

I have permanent tinnitus from one shot of a .357 from a snubby in a small room.

They are all loud at the muzzle. But there are other factors - are you in an enclosed space? A hallway? Is there sound dampening material (carpet, soft furniture) or will the room reflect sound (hardwood floors, etc.)? Will you be standing near a surface that bounces back the pressure wave? And so on. Heck, had I been in an open room my tinnitus may have gone away after a few days. But that's the way it goes.

For these reasons, I don't make a choice based on the SPL of the gun.
 
#38 ·
Actually, I'm a bit surprised from one shot. The ear is pretty good at "clamping down" and protecting the inner ear from damage from one or two concussions. With repeated concussions, the defense mechanisms tire and the inner ear is unprotected. I used to shoot trap and skeet for hours without protection, as no one did back then. My ENTs have told me over the years that the reason I have severe tinnitus is from repeated concussions, exceeding the ears' natural protection. At any rate, I'm not going to start worrying over the effect on my ears when my and my family's survival is at stake...
 
#36 ·
Going to blow someone's brains across the wall in a life and death struggle, I'm not worried about a big noise. I don't even want ear protection: might need to hear something before the firing starts.

At the range the other day, just after arriving, I realized I'd forgotten to put the little orange plugs into my ears; the plugs I wear inside of the big plastic ear protectors. Never said I was smart. Took off my ear protectors to put in the little orange earplugs; I knew what I'd done by the third second, and couldn't get the ear muffs on before someone fired a rifle. It made me jump quite a bit. And hurt my ear. Mostly I was embarrassed by the 3 inch jump my hands made.
 
#39 ·
took my ears off at the range to talk to someone.....and then forgot they were not on my ears, but hanging on my neck. Realized my mistake just as I touched off a 158 gr .357 Magnum.....under a steel corrugated over-hang. Felt like someone shoved an ice pick in my right ear. Had a discharge of a .357 Magnum in a small room without hearing protection and barely felt it. The drywall absorbed the shock of the blast unlike the corrugated metal which amplified it.

....if you want to speak with me....speak in my left ear. :image035:
 
#46 ·
Felt like someone shoved an ice pick in my right ear. :

Boy do I know what you are talking about. Except it wasn't firearms - but instead being an aviation ordnanceman squatting between CAT 1 & CAT 2 on an aircraft carrier, with F4 Phantoms in full afterburner. Even with the 2-way communication headset/hearing PPE we wore, it still hurt like you said an ice pick.