I'm ex-military and I have already lost half my hearing serving my country.  Seems when SHTF, the last thing you are thinking about is putting ear plugs in.  The hearing I have left is very valuable to me.

I had a Bushmaster M4 version with a mini-Y comp for self-defense and a SHTF rifle.  This was the loudest thing I have shot.  Even with hearing protection, this thing sucked.  

I like the carbon pistols, but I assume the noise from on of these will dwarf the noise from my old M4 with the mini-Y?  I mean, is this something I am going to kill my hearing if I ever had to shoot it in an emergency without hearing protection?

Say What? Makes no difference what brand AR pistol you are going to shoot, without hearing protection you will want to cry after the second or third shot. Home self defense?? with one of these is not the choice of most. Besides the flash at night, the unbelieveable noise inside of a home or structure these make and the penetration the bullet will do, (completely thru the house end to end) bad choice. Use a good handgun your accomplished with, if X- mil  try a 9mm or a 45 of some sort. Last thing you want is to shoot at a bad person inside or even out side of your home with the home being the back stop and having a round go thru the house, hitting someone not aimed at. SOUND!!!!! no ears on and you will be deaf after third round,,, think about it. bullet case is about 80 percent powder, 7 inch barrell,, powder still exploding at exit of barrell......LOUD!  I have one, last thing I ever want to do is light it off inside without plugs and suppressors on.

A short barreled AR type weapon, be it pistol, SBR, or 14.5 w/ perm muzzle device, is going to be loud.  11.5" or 10.5" types are LOUD.  About the only thing you can do short of an NFA suppressor is the Noveske flash suppressor redirects some of the noise/muzzle blast downrange so it's not as loud to the shooter.  Might be worth a try.

BTW, you mentioned a "mini Y", almost any compensator or muzzle brake will dramatically increase noise to the back and sides of the muzzle, a real bad idea if you're trying to maintain your hearing.  I put a brake on a 16" barrel AR as a test, after that, I wouldn't shoot a 11.5/10.5 inch barrel AR with a brake even with earplugs AND earmuffs.

I'd like a good reliable carbine, either AR type or not, in .45ACP for just this reason.

Heh, heh, heh!  I took mine to an indoor 30 yd range on the Gulf Coast and after a couple of minutes the staff came by and politely told me to pack it up.  When I had arrived, they had asked what I was shooting so I said 'pistol'.  They didn't ask what the caliber or model was!  I think they passed a kidney stone when someone asked and I said the round was a 7.62.  Maybe they thought I meant 7.62x51???  Oh well, I had gone through a couple of mags by then so I wasn't too bummed about having to leave.

Thanks for the info.  I figured these were loud, just wondered how loud.  I thought it would be fun to shoot, but I think I would rather have a full size rifle that will not blow my ear durms out.

For defense, I was only figuring in an extreme emergency, like I could not get to any other weapons.  I keep a 12 gauge loaded with bird shot for the home invasions and a .45 acp for backup.  And if it really hits the fan, aka hurricane/terrorist, I have a Mini-30 which will soon be replaced by a M1A Scout or M15 in 6.8 cal.

My Carbon Busy Pistol seems louder then my M2HB 50 Cal.....

I double up. ear plugs and then muffs on top.

I always keep some hearing protection with the pistol just in case.  If I have to go for the gun, they are right there.  Takes 1 second to slip on.  Any other pistol and I might decide that my future hearing was less important than my immediate security.  With the AR pistol it's just too loud to even consider firing without protection.  However, I've been been in the room when a .38 went off indoors and that was plenty loud without hearing protection too.

Mine is a loud MF!!!

z