.22 cal SPL measurements

**Rich Jura** · **03-19-09, 08:42 AM**

Last weekend I attempted to measure a variety of .22 cal rounds. At my disposal I had a Galaxy 140, Extech and a Terrasonde Audio Toolbox. The results were interesting to say the least, there was no consistency amongst the readings. They varied by as much as 20dB for the same round. I don't think any of them are capable of doing a sharp short burst of high SPL. I'm digging out an old Ivie hand held 10 band RTA and seeing how that does.

Later
Rich

**joorge** · **03-19-09, 10:06 AM**

Your equipment is not capable of accurately measuring the event. Too slow. You should be around 155-160dB for a pistol and 140 for a rifle. It depends on barrel length and ammo used. Measurements will be very consistent.

**Ricci** · **03-19-09, 10:15 AM**

For a .22 LR? That seems way high to me. I'd guess more like 125db or less. My snare drum is louder than a .22. A big high power rifle round like a .300mag is around 160-165db.

**Rich Jura** · **03-19-09, 10:35 AM**

I was expecting approx, 110-115dB @ 3ft, was getting 92-105. If I recall correctly the Ivie was supposed to be able to handle this type of measurement. I didn't expect the Galaxy to do it but the Terrasonde Toolbox @ $1300+ I thought should have been up to the task.

Later
Rich

**joorge** · **03-19-09, 11:00 AM**

The microphone is a weak link, too. Plenty of info on the net if ya want to pursue it. The B&K 2209 sound meter with a B&K 4136 microphone is one of the few combos capable of accurately performing this type of testing. I think there is one other.

The numbers I quoted were from a proper test of a Walther P-22 and a Ruger 10/22. Both were using CCI standard velocity ammo. Your results should be within a few Db of these numbers if you follow the Mil-Std 1474D protocol.

Edit to add that the dB levels quoted are for the specific arms and ammo cited. SPL levels will change some depending on equipment and ammo used. The particular combos cited are common platforms used for testing purposes.

**Rich Jura** · **03-19-09, 11:12 AM**

joorge

Do you know at what distance those readings were obtained at? I was measuring @ 3ft would I be better off using an Earthworks TK-30?

Thanks
Rich

**joorge** · **03-19-09, 11:28 AM**

1 meter, 90 degrees off axis, level with barrel. I don't recall the distance from the ground, close to 4', maybe. Google "Mil-Std 1474D" and you should be able to find all of the protocols.

Again, you won't get anywhere without the proper equipment. The issue is that most (almost all) meters and mics are unable to capture the entire spl curve from a gunshot. What you are getting is a piece of the curve that does not include the peak that you really want to measure.

There is little need for equipment capable of this type measurement, so it's not common. I'm not sure any current equipment is capable of these measurements. Most of it is purchased used and sent in for calibration.

Have fun, but it's gonna take very specific equipment and numerous thousands of dollars to get it right.

**Rich Jura** · **03-19-09, 12:41 PM**

Thanks...........I'll give it a shot.

Rich

**Ricci** · **03-19-09, 04:54 PM**

Quote:

Rich Jura wrote:

I was expecting approx, 110-115dB @ 3ft, was getting 92-105.
Later
Rich

That sounds about right.

There is absolutely no way that a .22 cal LR round no matter what it is chambered in is 160db at 3ft. It is very easy to tell this from years of being around loud music and hunting/ shooting. Maybe 1" from the barrel. You can easily Google this stuff. A very high powered rifle round like a 30-06 or .300 mag is in the 160db range at 1 meter. If a.22 was 160db, how loud would that make something like a .338 REM Ultra Mag or a

.50cal? Which are complete orders of magnitude louder?

**joorge** · **03-19-09, 08:01 PM**

I said it was 155 to 160. Not 160. Just looked a test up. 156.75. this is a short barreled pistol. It matters. M16's are over 165. .308 about the same - maybe 167-169. 300 WM = a little more.

I'll leave it to you experts.

**Ricci** · **03-20-09, 01:37 PM**

We'll just have to agree to disagree. I've looked at various data and they are all over the map depending on barrel length, ammo used, test conditions, equipment, etc. I've seen anywhere from 116db-160+db quoted for a .22. I just tend to agree with the lower values quoted.

In my experience they don't have the concussive pressure wave and ear splitting "crack" that hits you in the face and chest that a larger more powerful round has.

Can you link me to the tests you are looking at?

Sorry about high jacking your thread Rich.

**joorge** · **03-20-09, 04:17 PM**

There are lots of people "testing" with RS meters and posting the results as factual on the net. Some people use golden ears and kick drum calibrators. Very few people have the resources to accurately measure gunshots.

You don't seem inclined to accept accurate information and I have no inclination to prove anything to you. Silencer Research has lots of accurate testing for anyone interested.

**Ricci** · **03-20-09, 08:16 PM**

No need to be rude. Nice jab with your "golden ears and kick drum calibrator" comment, though I've never heard of a kick drum calibrator. That's a new one for me. All I asked for was a link to who does have the "accurate information" since I didn't know and accepting someone's word is tough for me unless I know them, being the internet and all. Recreational shooting and hunting has been a lifelong hobby for me. I didn't expect this to turn into a debate.

**Pinhead-227** · **03-20-09, 08:23 PM**

I have to agree, though, that a .22LR in a rifle can't be anywhere near 160 dB or even 150 dB. Maybe in a pistol with a 2" barrel, but definitely not in a rifle. Now a .220 Swift or a .30-30 Winchester, on the other hand, is another story altogether.

**joorge** · **03-20-09, 11:46 PM**

No, what you did was hijack the thread and question me and my information without a clue as to what is correct. You are causing confusion and posting misinformation.

You don't appear to know enough about the subject to look it up. That's rude and why there is so much bad info on the net. Not only that, you don't seem willing to stop long enough to get the facts.

Did you look at the testing at Silencer Research? I guess not. You are welcome to your opinion, but it is in opposition to repeatable, verifiable, scientific testing.

I quoted 2 specific weapons, the ammo used, the testing protocols used and the resulting SPL. I did this to inform the OP, not to open a debate about something that is really not debatable.

Since you have trouble "accepting someone's word", you will need to do some work on your own.

BTW, I went over to Silencer Research and looked at some of the testing. Here's part of the testing protocol used:

"....The tests were conducted using the B&K 2209 sound meter with a B&K 4136 microphone calibrated with the B&K 4220 Pistonphone. All equipment has been certified and tested so that it can be traced back to the N.I.S.T standards. The meter and weapon are also placed in accordance with Mil-Std 1474D protocol...."

This particular test resulted in the following SPLs using CCI Standard Velocity ammo.

Walther P22 - 156.0 dB
Browing Buckmark - 154.5 dB
Ruger 10/22 - 140.4 dB

Of course, I could be making all this up.

**Ricci** · **03-21-09, 12:43 AM**

I was not trying to personally attack you or the advice that you gave the OP about the need for a very high quality test rig for measurements like these. Perhaps it came off that way. I did try to look up .22 tests and had in the past just for curiosities sake. I looked at the MIL spec document that you posted. I didn't know to go to the Silencer Research forum, or know that you got your info from there. You didn't post that until later and I had never found that site in my searches.

After looking at some of the data at the Silencer Research forum and the aforementioned test equipment and prcedures, it's hard to argue with. Close to 155db out of a .22 cal just seemed incredible to me and honestly it still does. What it makes me wonder about is the actual loudness of other sharp impulsive sounds and the ability of most set-ups to record them, if even a paintball gun is close to 120db.

**joorge** · **03-21-09, 01:31 AM**

This type of sound is unlike any other sound you may have SPL experience with. The SPL's are routinely reproduced within a few dB's by other professional testers, so they are pretty accurate for a specific gun/ammo combination.

The numbers I quoted would change with ammo selected and barrel length. It also would be quieter if measured at the shooters ear instead of at the end of the barrel. People standing behind the shooter would experience even quieter sound.

Once you put the meter away and ask for loudness opinions, things change a lot. Just like with home audio, not everyone hears the same thing. Many people think a significantly louder shot is quieter if it's tone is more pleasing.

Back to the original topic - The primary factor in measuring the gunshot is the response time of the equipment. 50 microseconds (not milliseconds) or less is necessary to insure that you catch the peak. Otherwise, you are just measuring some unknown part of the curve. You may be catching the down slope of the curve with a slow meter. You also need equipment that will survive the blast.

I don't know about the ability to evaluate the sound with software/sound processors. Way over my head. I'm just guessing ya need to capture 5 or 10 milliseconds containing around 200 samples with equipment capable of 100kHz to get meaningful results.

**joorge** · **03-21-09, 01:44 AM**

You can probably rest easy with the paint ball gun. The military uses 140 dB as determined using the mil spec as the point that hearing protection is required.

It's a bucket of worms cuz your ears aren't where the sound was measured. They accounted for most of that and basically generalized for "typical" conditions. It's a good guideline to avoid hearing loss.

The thing to worry about is the protection afforded from high power rifles by ear muffs. 165+ dB is attenuated by 15-20 dB by most muffs. Not good enough. Read the specs for the muffs or use plugs and muffs.

Edit to correct the range of attenuation provided by most common protectors.

Foam Plugs - 29-32
PVC Plugs - 25-27
Muffs - 20-30

**Ricci** · **03-21-09, 09:38 AM**

I always use plugs and muffs. I've got one friend who doesn't bother with any protection at all no matter what I say to him

I've been around a lot .22 shots and subjectively they aren't very loud to me. A good metal on metal clang, or like I said earlier a solid rim shot on a snare drum seems louder to me. The tests say otherwise. Maybe this is because of the different distributions of energy across the frequency spectrum? A snare hit is right in the midrange where our hearing is most sensitive. I'm guessing that the majority of the .22 shots energy is going to be a low frequency shock wave effect off of the bullet going supersonic, and that the sound of the blast, or report is not as intense? That would make it seem less loud than it is.

**joorge** · **03-21-09, 12:04 PM**

I don't know why a rim shot could not be louder than some gunshots. Most gunshots register the highest SPL around the muzzle in the 100-3,000 Hz area.

Most 22 rifle/ammo combos are hearing safe or very close to it. It would be reasonable to perceive them as relatively quiet.

The supersonic wave is a component of the downrange sound, but is not a factor with the CCI standard velocity ammo we have been referencing as it is sub-sonic.

I am uncertain when the ss wave attaches to the projectile or if it is even measured by the mil spec protocol. It may appear a bit later than the test period covers. I do know that ss ammo tested in the 22 does not increase the SPL more than a few dB.

**Ricci** · **03-22-09, 01:31 PM**

Quote:

joorge wrote:

I don't know why a rim shot could not be louder than some gunshots. Most gunshots register the highest SPL around the muzzle in the 100-3,000 Hz area..

Perhaps the test rigs used to determine the loudness for other rapid impulse type sounds have not been suitable for the job. I don't think an RS meter is going to be adequate. I'd be interested to see what a concert snare drum, or a heavy hammer on chisel type of blow would measure on a test rig like used by SR. Could be eye opening.

Quote:

joorge wrote:

Most 22 rifle/ammo combos are hearing safe or very close to it. It would be reasonable to perceive them as relatively quiet.

The supersonic wave is a component of the downrange sound, but is not a factor with the CCI standard velocity ammo we have been referencing as it is sub-sonic.

I am uncertain when the ss wave attaches to the projectile or if it is even measured by the mil spec protocol. It may appear a bit later than the test period covers. I do know that ss ammo tested in the 22 does not increase the SPL more than a few dB.

Wouldn't the SS "boom" attach as soon as the projectile becomes SS? Right after it leaves the barrel? The expanding gases from the propellent itself are going to be SS are they not? Perhaps even with a subsonic load? If the tests indicate that the difference between SS and subsonic ammo is only a few db's then that would point to the sonic boom not being the only reason for the apparent extreme loudness of even a small round. I was just thinking that since a SS wave is a very low frequency that is more of a physical feeling or pressure than a distinct sound through the ear that this would explain how something could seem relatively "quiet" but still be very loud. Hmmm.

Do you know of anywhere that captures the spectral content of a gun shot?

**joorge** · **03-22-09, 03:33 PM**

I donno when the wave attaches. It doesn't for sub sonic ammo like CCI standard velocity. You're measuring the loudest impulse at the muzzle when using the mil spec method, whatever that may include.

I looked at a test that used both CCI Standard Velocity and CCI Mini Mags in a Ruger 10/22. The subsonic Standard Velocity SPL was 139.4 and the super sonic Mini Mags were 142.1. I don't know if increased SPL is attributable to additional powder, ss crack or some of each.

Lots of good info comes from Finland. Go to the BR-Tuote site (http://guns.connect.fi/rs/index.html) and scroll down to the "Scientific:" area. That should keep you busy for awhile.

**Anechoic** · **03-23-09, 04:17 PM**

As someone who has done gunshot measurements, it's not the microphone that will be the weak link, it's the RMS circuit in the meter (and in particular the averaging time you select). You will get different results if you use "slow" "fast" "impulse" or "peak" time weighting. For gunshots you will generally want to use "impulse" or "peak" time weighting although there's not really a consensus in the U.S. about which is more appropriate.

The TerraSonde (which one? The Toolbox or Toolbox Plus?) should be able to handle it using Peak or Impulse weighting.

Even at very close range using "peak" weighting, 150+ dB/dBA for .22 sounds high.

(fyi, the project I did gunshot measurements for is still winding it's way through the New Hampshire appeals courts so I can't talk about specifics but I can talk about things in general).

edit: I should clarify that the mic can be limiting in the sense that inexpensive mics may start clipping over 130 dB or so, but again I wouldn't expect that to be a problem with a .22.

**joorge** · **03-23-09, 08:49 PM**

I'm glad to see an expert arrive to help out. Would you comment on the minimum rise time necessary for the microphone to capture the event? What is the rise time on your mic?

Would you have the SPL for any 22 in your files? If so, what is it? What gun/ammo and equipment did you use and where was it positioned? What testing protocol did you use?

I'm not asking about your court case. Just some info based on your other testing that would help me understand why the info I provided is incorrect.

**Anechoic** · **03-23-09, 11:36 PM**

Quote:

joorge wrote:

I'm glad to see an expert arrive to help out. Would you comment on the minimum rise time necessary for the microphone to capture the event? What is the rise time on your mic?

Would you have the SPL for any 22 in your files? If so, what is it? What gun/ammo and equipment did you use and where was it positioned? What testing protocol did you use?

I'm not asking about your court case. Just some info based on your other testing that would help me understand why the info I provided is incorrect.

Mics aren't rated for rise time, the rise time is a function of the electronics. A meter with a "peak" time weighting setting should be able to accurately capture the full impulse (within the audio bandwidth) of a gunshot.

I don't want to comment on the specifics about what I've done*, but I will say that I have never directly measured the output from a .22. However, I've fired .22s along with high caliber weapons and I've measured the sound from higher caliber weapons. The noise from the higher caliber weapons was noticeably louder than the .22 and none were over 150 dB at close range with impulse time weighting.

Paul Schomer is probably the leading expert in the USA when it comes to small arms noise data, if anyone has data that I would trust with no question, it would be him. When I get a chance, I'll go through my library to see if he has public papers with protocols and data that I can direct you to.

* Like I said, this is winding it's way through court and if I give an overly casual explanation or skip a step to simplify, if a lawyer finds it they can attack me in court by saying "Mr. Singleton, you said in your testimony that you did xx and yy but in this posting on hometheatershack.com you said you only did xx. Why are you lying" etc.

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