Nothing to be sorry for, but thanks I guess. My hypersensitive hearing has made my career as a luthier possible, at least in part. I can hear even very subtle changes in tonal quality and power from an instrument, making adjustment to meet a player's needs relatively easy.
Seems I forgot the actual numbers for CCI SV, sorry about that. Just looked it up again, and found this very informative paper by the widely recognized top expert in the field of firearm sound suppression, Philip Dater:
www.larsondavis.com/ContentStore/mktg/LD_Docs/Firearm_Sound_Briefing.pdf
On page 57 (at the default PDF zoom on my browser anyway) there's a small chart showing A-, C-, and Z-weighting (Z = unweighted) metered sound pressure in dB of CCI SV from a Ruger Mk II pistol with a bull barrel, as measured using L&D equipment, the best suited metering ever devised for this very short impulse noise. A = 138.6dB, C = 137.4dB, and Z = 142dB. For one comparison, also listed in that file is a P228 firing a 9mm cartridge, metering around 160dB.
Later in the same document, Dater shows a set of values measured at 1 metre to the side of the muzzle of a 10/22 with CCI SV. That average was 137dB. It is followed by increasing distances in various intervals.
Liberty Suppressors uses the same metering tools, and in a series of tests they ran for general education years ago, they found a pop can being cracked open was 110.5dB, the plastic lid of a CCI SV 100-round plastic box lid being snapped in half metered at 117.2dB. They were being a bit silly and included a couple of other sounds, but those two seem relatively replicable, and were metered at the standard distance of 1 metre.
Industry standard suppressors are generally compared using CCI SV from a 10/22. The action noise/ejection pop is much lower than the muzzle noise, so the semi-auto function doesn't get measured. The very best commercial suppressors have managed to meter the odd shot at about 109dB, here and there, but averages tend to bottom out at around 112dB. The bulk of US-made commercial .22lr suppressors tend to range between about 113dB and 120dB, with testers reporting that anything above about 118dB tends to be a bit hard on the ears, uncomfortable, not painful, if not wearing ear plugs.
This little description of decibel measurements comes from one of the better answers on Quora:
1db is roughly what a person can detect in terms of an increase in volume.
+10db is an apparent double of volume. This means that a person listening to the sound would say that it is twice as loud every 10db.
However, the energy in the sound, that is, the destructive power of the sound DOUBLES every 3db. In fact, when you are preparing a sound system, to add another 3db of volume, you need to double the power of your amplifier (assuming the speakers are rated for the power increase)
So, a 30db drop is cutting the sound if half 10 times. Go ahead and try to fold paper ten times in half. That is the kind of effect. 30db is a VERY significant amount. Most hearing protection is less than 30db and the few that are more are rarely much more. My favorite ear plugs that I use to shoot, mow the lawn, etc are 25db and are VERY comfortable.
That matches the best explanations of decibel levels I've seen in a number of places over the years. The difference in noise between a pistol and rifle barrel is substantial, and the longer the barrel, the quieter the report, within reason. CCI SV generally stops accelerating at about 12" down the bore, with longer barrels actually slowing the bullet for the remainder of the bore. This varies depending on exact bore dimensions, surface smoothness, and twist rate, but in general it's safe to say that a 24" barrel is going to keep a CCI SV bullet subsonic, even in winter when the speed of sound drops substantially, while a pistol or very short rifle barrel may not. And the noise at the muzzle will drop considerably with the longer barrel, as most or all of the powder will be burnt and the pressure inside the barrel has dropped considerably, though it's still a few thousand PSI at the muzzle, when the bullet 'uncorks' that pressure.
According to Philip Dater, the maximum sound considered safe by US MIL-STD-1474D is 140dB. I'd suggest that's a bit high. And others in the shooting industry have often stated that 135-137dB are about the maximum. 140dB is double the sound pressure of 137dB. So I guess from the above measurements of CCI SV from a pistol barrel (he doesn't say the barrel length) is in the 137-142dB range, that would not be at all safe, but from a bolt rifle 24" long, it seems likely to be technically safe, if still annoyingly loud.
I shot an old bolt action .22lr once, when I was about 12 - our stepfather took us out to a gravel pit one afternoon to shoot a few times, just so we knew how to work a rifle... that ending rather quickly as neither me nor my younger brother was at all happy with how loud the thing was. No supersonic crack, so I guess they were subsonic cartridges. But damn, I remember that hurting a lot, my ears ringing for some minutes. That barrel had to be at least 22" long, if not longer. I remember struggling a bit to keep the muzzle up and hold it on target - a beer can, which I missed, though I was a crack shot with my .22" break-barrel pellet rifle and had taken down lots of small game with that.
I guess I'm left a bit puzzled by these various perspectives and data points. Gunfire is loud. Even .22lr is loud any nearer than about 1/2 block away, to my ears anyway. I had custom moulded silicone ear plugs made years ago, for 10 metre air pistol training and competition, the ~495fps pellet from my Pardini pistols being a bit much, indoors, and the crack of some fellow club members' Morini pistols being considerably louder as they tended to tune them up to around 525fps with 7gr pellets. I'd have a headache if I didn't wear those ear plugs. Only one other guy at the club seemed to wear hearing protection - he's currently on our national pistol team in both 10m AP and in .22lr pistol.
