Tuesday, March 17, 2009

Airgun sound level measurement

by B.B. Pelletier

I promised this report last September and Kevin reminded me last week, so here it goes. We're all concerned about the sounds our guns make. Sometimes, we make analogies about how loud or quite a gun may be, but these are rough approximations at best.

This information is extracted from an article that ran in Airgun Revue #4.

Sometimes, we buy "sound meters" that claim they will give us the intensity of a sound, but the meters available across the counter these days just aren't the right tools for the job. In his recent video, Airgun Reporter Paul Capello gives you a sound level for the Hammerli Pneuma. Paul says the gun sounds loud to him, yet the number his meter gives is 104 decibels. Actually, that is really very quiet and would be more the level of a low-powered Walther 55 target breakbarrel. The Pneuma is really more like 123 decibels, but Paul's meter doesn't show that high a rating because it isn't an impulse sound meter.

I was at Crosman a few weeks back and they were testing a very loud pneumatic gun in a room with concrete walls about 10 feet apart. The sound meter registered 118 decibels for what I felt certain was over 130 decibels of sound. That meter was also not set up for impulse sound measuring. Everyone in the vicinity of the shooting was wearing hearing protection.

I'm saying this because I had a professional sound tester in attendance at the 1998 Big Bore Shoot at Damascus, Maryland. Steve Lewis, a state-certified audiologist, had performed sound testing for the federal government and published papers on the subject. When he offered to test some of the big bores we had at the shoot, I welcomed him. On the day of testing, we expanded his test to include regular airguns, as well.

Steve used a calibrated "type 0" three-scale sound level meter (SLM) to measure these sounds. His equipment could measure the peaks of the impulse sound, which is what all those inexpensive "type 3" SLMs you buy at Radio Shack are cutting off when they give their numbers. The numbers Steve recorded were much higher and reflected the potentially damaging impulse sounds that OSHA measures to gauge the need for hearing protection in the workplace.

Steve's SLM also froze the readings on all three scales, so you didn't have to watch the meter all the time. On a low-cost SLM, someone has to watch the meter as the noise is generated. The number that appears on the gauge is just temporary.

This testing was conducted outdoors in an open wooded area. Steve set up the pickup 90 degrees to the right of the muzzle and exactly 10 feet away. If the pickup was placed in a different spot, all the readings would change.


Sound level information gathered at the 1998 Big Bore shoot at Damascus, MD. Courtesy Steve Lewis.


I find the above chart fascinating because of all the relationships it shows. Look at the Career 707 Carbine, for example. You would call that rifle very loud, but how many of you would be able to relate it to a Sharp Ace Hunter? And for those who aren't familiar with the Sharp Ace, it's a multi-pump pneumatic that has about double the muzzle energy of the Sheridan Blue Streak. We didn't get a number for the Blue Streak, but my gut tells me it might come in around 118-120 dB.

Look at the big, brutish Webley Patriot. Many would insist it would be louder than a Beeman R9 in .177, but on this day the numbers didn't work that way. My guess is that the R9 had a very loud powerplant.

Look at the Beeman Crow Magnum. I've had several shooters tell me that rifles with gas springs make an extra crack when they fire, but I've never been able to hear it. Apparently, the SLM could!

Notice the large difference between two Beeman P1s. Caliber, alone, does not account for this much difference.

BB, please relate all this to something I KNOW!
I'll try, and then you'll see why I can't. Do you know how loud a .22 long rifle cartridge sounds? Several of you have raised your hands, but you moved too soon. The sound will vary GREATLY depending on the length of the barrel of the gun from which it is fired and the type of cartridge you fire. What I CAN tell you with some degree of certainty is that, when fired from a 20-inch barrel, a .22 long rifle high speed cartridge will exceed 140 dB, if measured exactly like Steve set up his measurements. So, nothing on that chart is as loud as a .22 long rifle.

Some of you are saying that I'm wrong about that. You own a Career 707 and shoot it next to your Ruger 10/22, and it sounds about the same.

Sorry to tell you, but your ears, like the cheap type 3 SLM mentioned earlier, are degraded and cannot sense the peaks anymore. Shoulda laid off the Metallica! Curb yourself before the other elevator riders hear you doing rude things because you are assured they are completely silent!

Is this an eye-opener, or what?
I've known about this since Airgun Revue was published back in 1998. Whenever I brush off a sound meter test, this is what has been behind it.

Some of you will argue that if I give you a number, AT LEAST it will be relative from one airgun to another. Yes, it will be, but standing in ice with your left foot and boiling water with your right does not put you in the comfort zone. By that I mean that being imprecise in sound measurement does nobody any good. If the 118 dB that Crosman was measuring was really 136 dB, what does it matter?

OSHA says the threshold for pain from impulse sounds is between 130 and 140 dB, depending on the person. Pain equates to hearing damage. With impulse sounds it is the combination of the numbers of loud sounds and their intensity that affects a person's hearing. Therefore, knowing whether something is 118 dB or 136 dB really does matter.

At any rate, that's my report on sound level testing.

61 Comments:

At March 17, 2009 6:46 AM, Anonymous Mr B. said...

Morning B.B.,

The springer numbers surprised me. I wouldn't have thought they would have been that high. However, back in the day, hearing protection wasn't considered as big a deal as it is now, which is why mine isn't as good as it should be.

Looking fwd to the Marauder review.

 
At March 17, 2009 7:11 AM, Anonymous Scott in Hawaii said...

Good morning B.B.,

Very good report as usual. It would be interesting to see how much louder the rifles have gotten in 11 years. Also would like to see the difference between a shrouded & un-shrouded barrel.

Off topic; When will you post a prelim report on the Marauder? How did Jim Chapman get a review out before you?

Aloha
Scott

 
At March 17, 2009 7:30 AM, Blogger B.B. Pelletier said...

Scott,

My Marauder report will probably begin in April. Jim Chapman has a prototype Marauder. According to what Crosman told me, he wasn't supposed to publish anything until the gun was ready for production, but there may have been a mixup, since he doesn't have the final article.

B.B.

 
At March 17, 2009 7:36 AM, Anonymous Mr B. said...

Kevin,

Thanks for your well thought out comments about your S410. I'm hoping that the Marauder will be the Savage 110 of the PCP rifles.

 
At March 17, 2009 8:01 AM, Blogger CJr said...

Interesting post. You'd think technology would be up to it by now but then I guess there's not much of a civilian market. A few more years of "Metallica" and it won't make any difference anyway. In a generation or two our heirs won't need hearing protection. (c;

I didn't really have anything constructive to say but I wanted to use the word verification "ovospine" real bad.

-Chuck

 
At March 17, 2009 8:27 AM, Anonymous Anonymous said...

B.B.This was a great piece on how we percieve things,as opposed to how they actually are.I bought a TX 200 in.22 because of the shrouded barrel to take care of pests without alarming my neighbors.The Navy did'nt care about ear protection in 1966 on a 40 mm mount,nor I for many years with loud Harley pipes.How do you think the TX 200 would have compared ? Thanks,Jersey Boy

 
At March 17, 2009 8:27 AM, Anonymous Anonymous said...

Are these measurements A-weighted? It's pretty tough to talk "loud" and "soft" without some spectral data.

 
At March 17, 2009 8:35 AM, Blogger B.B. Pelletier said...

Jersey Boy,

I think the Mark III TX 200 would come in at around 107-109 dB.

B.B.

 
At March 17, 2009 8:39 AM, Blogger B.B. Pelletier said...

Unlike the less-expensive SLM, the inpulse circuitry does not RMS average the sound energy, nor does it apply any of the weighting scales. So, no A-weighting was done.

B.B.

 
At March 17, 2009 8:43 AM, Anonymous Phil L. said...

Yes, I've also seen some sound measurements - but have always known to take them with a grain of salt.

I'll suggest one sound measurement I suspect many of us would appreciate. I'd like a metric that reliably answers the question "Can I safely use this particular airgun in a typical basement 10m range without earplugs?"

Since this is where most of my shooting takes place (and I suspect many you at least do some testing in such an environment), this would be useful to know. I'm not looking for magnum power, so knowing a potential airgun purchase won't have me needing ear protection would be helpful.

 
At March 17, 2009 8:47 AM, Blogger B.B. Pelletier said...

Phil,

I don't know what kind of measurements you would get, but practically nobody (I say "practically" to allow for one or two crazies that might exist) at a 10-meter pistol match wears hearing protection. The guns just aren't that loud.

B.B.

 
At March 17, 2009 9:08 AM, Blogger kevin said...

B.B.,

Thanks for the article. Your experience about where you stand (the sound metering equipment was 90 degrees) in relation to the muzzle of the gun can't be overemphasized in my opinion. Behind the gun or off to the side in front of the gun is a dramatically different volume.

Uh-OH. A-weighted, spectral data. I see formula's in our future.

This is very interesting and at the same time confusing to me.

I have to assume that most spring rifles that showed up at the Damascus Big Bore Shoot were tuned. A tuned spring gun is quieter than an untuned rifle in my limited experience. So comparing an untuned gun with a tuned gun may explain away some of my confusion. My old ears could also be playing tricks on me because my tuned R9 was twice (subjective) as loud as my tuned R7 and the db scale shows it's only 5% louder. In other words, if I could synchronize shooting two of my R7's the R9 would have drowned out the sound of the R7's.

I don't know anything about decibal scale but it must not be a constant curve because although the scale shows a career 707 carbine 20% louder than an R7, my ears told me that ten R7's shot in unison could be drowned out by one career 707.

The scale also shows an fwb 124 is louder than an R9? I need to get my ears checked.

kevin

 
At March 17, 2009 9:23 AM, Blogger FRED said...

As I recall, an increase of 3 db means the sound appears twice as low to the bystander so a gun measured at 118 db is twice as loud as one measured at 115 db. I may be wrong here but the decibel scale is what's referred to as a logarithmic scale.

If you think Metalica is/was loud, The Who concert I went to back in 1980 was absolutely painful. The security guards at the foot of the stage wore industrial hearing protection. I kept my fingers in my ears for two damn hours! What a waste.

BB - do you have plans to test the Crosman Challenger PCP? This seems for me the ideal starter 10m rifle since I'm already set up for the Discovery.

 
At March 17, 2009 9:40 AM, Anonymous Anonymous said...

Loudness and intensity aren't the same thing. Plain ol' dB just measures intensity. A sustained low sound at 80 dB wouldn't bother us much, nor a really high sound. But sustained sounds in the middle might almost hurt at 80 dB, or at least prove annoying.

Things like "A-weighting" and "RMS" attempt to tweak the numbers to be more meaningful to us, the people hearing sound. (A-weighting takes into account the hilly frequency response of human ears; RMS measures average rather than peak intensity of sound.) Without these tweaks, dB values don't mean a whole lot. They mean something, surely, but don't bet your life on 'em.

 
At March 17, 2009 10:08 AM, Anonymous Anonymous said...

B.B.,
Do you happen to have some frequency spectrum data? It would be very interesting to know what dominant frequencies are for all those airgun sounds. I heard the loudness is not always proportional to the sound pressure level.

Alan

 
At March 17, 2009 10:25 AM, Blogger B.B. Pelletier said...

Fred,

Yes, I do plan on testing the new Challenger PCP target rifle as soon as it becomes available.

B.B.

 
At March 17, 2009 10:35 AM, Blogger B.B. Pelletier said...

Everyone,

When Steve performed this test he told me that even many audiologists working at OSHA do not understand how impulse sounds work. That was his area of expertise.

The weighted scale is more meaningful for sustained sounds, as he explained it, but it clips the tops off the impulse sounds.

And, no, I don't have the frequency information.

B.B.

 
At March 17, 2009 11:11 AM, Anonymous Mr B. said...

B.B.,

I've found the numbers interesting, but I don't know what 80dbs or 105dbs really sounds like. Yes, I know what a .22 long rifle sounds like, sort of--re your comments on barrel length,etc., but how do we relate these numbers to our shooting without actually hearing the sounds?

 
At March 17, 2009 11:25 AM, Blogger B.B. Pelletier said...

Mr. B,

List a few of your guns.

B.B.

 
At March 17, 2009 11:40 AM, Anonymous Mr B. said...

B.B.,

RWS 35 and 350 Magnum, Benjamin Discovery, Talon SS, Benjamin 392 Crosman 1077 and 1377. Thanks

Mr B.

 
At March 17, 2009 11:46 AM, Blogger Lloyd said...

B.B.
Very valuable information for all of us. I've used inexpensive meters before and certainly won't trust them anymore.

Just for info, I have an engineer's pocket ref book and it says a difference of 3 decibels is barely perceptible, 5 is clearly perceptible, and 10 sounds twice as loud.
Unlike a cut on a finger, our hearing can't heal itself.
Lloyd

 
At March 17, 2009 11:51 AM, Anonymous twotalon said...

What db is....
Decibels is a convenient way of measuring either power or amplitude of values that can be either very large or very small. Much more convenient than writing out very long numbers.

Db is a log function. it can be used to compare the difference between amplitude or power (not the same thing) of two different values.

Let's say you have two different amplitudes with one being 10 times the other. There is a 10db difference between them. If one value is 100 times as large as the other then there is 20 db difference between them. It's just a way of measuring a relationship between the two.

Now to get an actual number that represents the VALUE of a db reading, you have to attatch a reference point to it so that the number being read is compared to a known actual value.

I don't know what the standard reference is for audio, but I do know it for radio frequency....
This is where dbm comes into play...that's decibles in relation to a 1 milliwatt standard. This way you can relate db to actual power .

So you can use db for all kinds of things . It defines relationships and measures values depending on how it is applied.

In case you wondered how great the silencer on the Whisper works....
Reducing the noise by 53% is only reducing the noise by about 3 db. That amount of difference is barely discernable to the human ear.

twotalon

 
At March 17, 2009 11:55 AM, Blogger kevin said...

Thanks Everyone,

This makes sense now to someone dense like me when it comes to db testing.

So a decibel scale is a logarithmic scale and a difference of 10db sounds twice as loud. Got it.

I think I like B.B.'s old scale. Hands clapping hard or car door slammed is easier for a simpleton like me.

kevin

 
At March 17, 2009 11:57 AM, Anonymous Anonymous said...

Interesting!
I found it surprising that my Slavia (I'm going to assume it would have about the same loudness as the R7) is quieter than my 853.
One thing that I would imagine enters into things is the difference in the sound quality of the different powerplants.
My 853 (single stroke pnuematic) has a discernible 'pop', whereas the Slavia has the traditional springer 'twang'.
I'm sure this is part of the reason for the 'apparent' perceived differences in the sound levels.
CowBoyStar Dad

 
At March 17, 2009 11:58 AM, Blogger B.B. Pelletier said...

Mr. B,

Your Diana 35 is probably putting out 112-114 dB.

The 350 Magnum is probably similar.

The Benjamin 392 is likely 118-120 dB.

The 1077 is probably 108-109 dB.

B.B.

 
At March 17, 2009 1:32 PM, Anonymous Anonymous said...

B.B.

Very interesting. What jumps out to me, like for somebody else, is how loud the springers are--only 10 db less than the Career PCPs rifle. Of course, the log scale of decibels is highly confusing and difficult to interpret. Also confusing is a standard of what is loud or damaging. I've heard the number 130 db associated with jet engines and rifle shots, but there was no accompanying information on where and how these sounds were measured. I wear massive hearing protection all the time to play it safe. I noticed the other night, though, that when the butt of the B30 contacts my earmuff directly, it is a heck of a lot louder than otherwise.

Don't forget the Air Force Edge for your reports. This is still the number one low-budget 10m rifle from everything I've seen.

Kevin, you write a mean review. Thanks. Wayne is vindicated. A few more questions. How is the trigger on the S410? How's the weight and ergonomics in the other positions besides benchresting? Is there anything about the shooting experience of the PCP to recommend it above springers other than its accuracy? Would it be fair to say that a springer will teach you how to shoot a PCP but not the reverse?

All, I feel bound to report progress in knife sharpening. After diligently honing a blade on the 15 micrograin and 5 micrograin sandpaper, I counted 6 small hairs shaved off the arm. It wasn't a shave that anyone would pay for, but hair has been cut! This could be the beginning of the end, or the end of the beginning.... Indications are good for the Russian leather razor strop and diamond paste up next.

Matt61

 
At March 17, 2009 3:15 PM, Anonymous Herb said...

RE: decibel scale

db = 10 * Log (Noise power level)

where log is base 10 log.

So a 20 dB difference is EXACTLY 100 times the power level in the absolute noise level.

a 10 dB difference is EXACTLY 10 times the power level in the absolute noise level.

6.99 is 5 times the absolute power level

3.01 dB is twice the absolute power in the noise.

Seems easy enough to me.


;-)
Herb

 
At March 17, 2009 3:24 PM, Anonymous Herb said...

RE: Articles on noise levels

http://www.nrahq.org/youth/enews/enews_06_summer.pdf
page 3 of PDF file

http://www.dangerousdecibels.org/hearingloss.cfm

Herb

 
At March 17, 2009 3:26 PM, Blogger kevin said...

Matt61,

RE: S410

Trigger out of the box was good but had a very long first stage. The trigger has more adjustments but I've only shortened the first stage and I like it alot. Less pull than my tuned rekord on the R7. There is alot of info on disassembly/tuning of the S410 trigger but I think the trigger is great where I have it adjusted. You hit on something I overlooked in my rambling last night. Weight. Weight was a major factor in my choice of the S410 and choice of walnut stock and my choice of scope. I wanted a light gun to take into the field. My gun out of the box weighed 6.4 lbs (using a fish scale) and weighs a little over 6.9 lbs with the scope and rings using the same fish scale. This is an easy gun to shoot standing because of the weight and the ergonomics of the stock are in full use standing vs. bench resting. I've been shooting mostly from a bench since I'm still pellet testing at both short distance and long distance on medium power and high power.

Other than very good trigger, lack of cocking effort, multi-shot capability (with the 10 shot rotary magazine, 970+ fps velocity in .22 caliber without recoil, very light weight and unbelievable accuracy there is nothing that makes me recommend a pcp over a springer. ;-)

I must agree. I think a springer teaches the fundamentals of shooting period. I believe that learning to shoot a sensitive springer translates to better pcp and firearm shooting not vice versa.

kevin

 
At March 17, 2009 3:38 PM, Anonymous Mr B. said...

B.B.,

Thank you sir. Gives me a point of reference, but mouse fart quiet works also.:)

Matt61,

Are using some type of guide to maitain the angle of your edge? After to leather strop the hairs should leap off your arm. Please let me know where one gets diamond paste and micron "sandpaper"--Thanks.

Kevin,

Since you mentioned the word formula, I wonder about the relationship between the placement of the meter and the barrel.

Mr B.

 
At March 17, 2009 3:56 PM, Anonymous Herb said...

MR B.

RE: I wonder about the relationship between the placement of the meter and the barrel.

Noise Power falls off as 1/r^2

so 1/2 distance would have 4 times the absolute power in sound or about 6 dB.

See:
http://en.wikipedia.org/wiki/Sound_intensity

Herb

 
At March 17, 2009 4:03 PM, Blogger kevin said...

I must be psychic. I knew there was a formula in our future today.
(you know I'm joking right Herb?)

Mr B,

I'm the most unscientific person on the planet. The meter placement 90 degrees from the barrel makes sense if sound waves are like the pebble in a pond water waves.

kevin

 
At March 17, 2009 4:28 PM, Anonymous Herb said...

RE: 90 degrees from the barrel makes sense if sound waves are like the pebble in a pond water waves.


Yes sound is pressure waves in the air in a 3-D wave like 2-D ripples on a pond.

Herb

 
At March 17, 2009 5:15 PM, Anonymous Volvo said...

Hello all, just stopping by.

I found today’s topic very interesting, but first some comments from having skimmed some of the other posts.

6’2” and 150 lbs? Seriously? I have not seen 150 since about 1983. As far as 6’2” I’d need stretched on one of those mid-evil racks. Thanks for sharing those self esteem boosting numbers.

Wayne – glad to see you’re enjoying firearms too. The .38 / .357 load is a great fun / plinker set-up and one of my favorites. Myself, I continue to thin my herd and noticed your number of recommendations while on the BOI at the yellow. Wow. Looks like you have not slowed down at all. You the man.

Kevin – Sounds like you’re enjoying the S410. I really fancy the FX Cyclone on medium power, so much that it inspired the continued selling I mentioned above. It is also now my lone PCP and worthy of the spot. As you noted in your review, the shot string \ chrony stuff is no big deal. I just feel foolish that I waited for so many years to try a PCP.

BG-farmer- glad to see you will still never be one of the lemmings. And thanks again.

Now for the meat and potatoes of the post.
Some of you may recall my intense noise fetish. The reason for this is the cliché about the best offense being a good defense. While legal to discharge an air arm in my locality, I have long doubted it would add to my popularity. Hence my limited exposure outdoors and my endless “how loud is it” inquires.
About a month ago I finally decided to take matters in my own hands and ordered a sound meter. The particular model I decided on was not a budget item, but not the highest end available either. The cost was comparable to a mid priced spring rifle. It is digital model that was listed as being the number selling unit by the vendor.
All - I would welcome feedback on the meter settings. ( twotalon, Herb, Bg Farmer. etc - please chime in)In order to be consistent, this is what I decided on – right or wrong:

MAX – this is the only one I am sure of. The alternative is a continual reading where as the MAX setting means it locks the highest number until reset. No need to watch it. Shoot, walk over and check.

FAST – this one I have no idea on. The other setting is SLOW. I picked fast because a shot is fast. Ok, stop laughing. On SLOW, the readings were consistently higher.

HIGH – is the last setting choice. Once again no idea if this is best, the alternative is LOW. I think this had to do with frequency?

Other variables:
I picked indoors for the testing, using the exact same spot each time. The other biggie is the distance from rifle to meter. I went with 3 ½ feet to the right side. Needless to say shooting closer means a higher reading.

A few results, an average of three shots:

R-1 Carbine .177 cal 89.1 db

HW30S (R-7) .177 cal 76.4 db

FX Whisper .177 cal 69.3 db

FX Cyclone .22 cal Low 73.5 db

FX Cyclone .22 cal Med 84.8 db

FX Cyclone .22 cal High 88.3 db

It seems great minds think alike. I used a Ruger Single Six with a .22 CB Long as a point of comparison. The reason for the CB is they shoot a 29 grain bullet at 710 ft per second for 32 ft lbs out of a rifle. Out of a six inch barrel I’m sure it has even less energy and is easily contained by my Beeman silent pellet trap.

.22 CB long from a 6” revolver 113 db.

Finally, I wish I would of bought the meters years ago. I’ve had dozens of rifles over the years I could of tested. Maybe not spot on, but shows the relationship well.

Volvo

 
At March 17, 2009 6:09 PM, Anonymous twotalon said...

Volvo....
You said it yourself...it shows a relationship......with that meter under those conditions.

No idea if it close to being right or if you are operating it right.

The rule for electronic test equipment...
It must give accurate readings for the kind of signals that it is looking at. You can use equipment that is better than necessary, but not equipment that is not good enough.
When calibrating electronic test equipment, the reference used for calibration must be 10 times more accurate than the unit being tested/calibrated.

twotalon

 
At March 17, 2009 6:25 PM, Blogger kevin said...

Volvo,

Great to see you back. you've been missed. Hope and pray all is well with your family.

You've probably seen my sales over the last 2 months on the site as well. I'm down to 6 springers and although I can't bring myself today to sell any of these wonderful spring guns some of them probably don't have long at this address.

I don't have a sound meter but your results are interesting. Quiet, lightweight, accurate, multi shot with minimal effort is my latest mantra. At medium power the S410 is quieter than my tuned R7. I know many people say that the S410 fully shrouded rifle (like mine), not carbine, on high power is as quiet as an R7 but that's not true. Maybe it is in .177 but my .22 caliber on high power is a little louder than my R7. I ordered a moderator for it last week and hope for some real stealth.

Don't stay away so long.

kevin

 
At March 17, 2009 7:17 PM, Anonymous Herb said...

Volvo,

RE: Sound meter

I don't know that much about sound meters, nor did you indicate the particular model which you bought.

In general your values are so much lower than the ones in BB's table that your meter must be averaging the sound over a longer time interval than the readings which BB reported. That is the real gist of the problem.

An organ could be made to emit the sound continuously so long as the key was held down. A piano would have a strong note initially, but it would fade fairly quickly. A gun shot is a severe spike. Each different kind of sound would need a "faster" meter to make the measurement.

The gist is the louder the sound, the shorter duration the exposure to not have hearing damage. Some sounds can be so loud, like a army howitzer, that one time exposure would result in hearing damage.

It seems to me that your readings are so far off the value's in BB's table that neither the absolute, nor the relative readings are particularly meaningful. For example you had 76 dB for an R-7 whereas BB had about 110 dB. That is a 35 db difference, or a difference of about 3000 in the absolute power level. So in essence the shot is happening must faster than the time interval over which your meter is integrating. For instance your meter could be averaging the sound over a 1 second window. The duration of the gunshot is much faster than that. This could possibly be compounded by another average value too. It is likely that the meter averages frequency bands. The guns shot doesn't produce noise over the entire hearing range with equal intensity. There will be certain frequencies that are much higher than others. Again, averaging would lessen the absolute value of the measurement.

So all in all, it doesn't seem like you bought the right meter for the job which was the point that BB raised in the blog article. You have to pick the right sound meter for the particular type of sound which you are measuring.

I'd guess that your meter would work fine for a rock concert, but not for measuring fast sounds in a narrow frequency band like gunshots.

Herb

 
At March 17, 2009 7:17 PM, Anonymous Anonymous said...

Matt61,I'm so sorry to have to put off any "how to"on the sharpening of cutting implements.sold my house,and with my bad back,moving/sorting has taken huge amounts of time& energy.most important to control sharpening angle...polishing a ground edge is easy with a good ceramic rod.a human hair is avg.100 micron.your sandpaper should work but may be distorting from flat.try only dragging the edge backwards at the proper angle.I don't know where things are going wrong for you...my left arm has little hair on top,and I can shave with a lawnmower blade.my e-mail is frankbpc@aol.com.I'll help any way I can! FrankB word ver:sandehe?

 
At March 17, 2009 8:19 PM, Anonymous volvo said...

Herb,
After re-reading BB’s blog it sounds like my numbers are more in line with the “bad” numbers that Paul and Crosman came up with. I will play with the settings and as a last result read the thick book that came with the meter. As Twotalon noted, I can at least rank them based on the results I have.

Kevin,
A LDC will help. With one on the Cyclone I get 68.8 \ 72.8 \ 75.8 versus the numbers posted above.
Do you have the rifle version of the S410? Does it seem big? That was BB’s first impression and my main reason for passing it up. As I recall it was not too heavy but “large feeling” if memory serves me.
I still have not graduated to a tank yet. Which one did you get?

Volvo

 
At March 17, 2009 8:37 PM, Blogger J-F said...

I was very surprised at the daisy 747 sound level, it's as loud as the R1 and louder than some of the other rifles.

J-F

 
At March 17, 2009 8:37 PM, Blogger kevin said...

Volvo,

Yes, I did buy the rifle version and not the carbine. Primary reason was fully shrouded barrel. Rifle is quiet compared to the carbine and everyone I read agreed on that.

Rifle doesn't feel "big" to me but I'm not a good judge because of a firearm background. Compared to my high power rifles and shotguns the S410 seems petite in length and weight. For comparison that you can relate to, my fwb 124 with the beeman muzzle brake is 1/2" longer and significantly heavier. The carbine version specs on PA's site says 34.84" and 44.5" for the rifle. My rifle measures 44 1/8".

I bought a new 4,500 psi tank set up. Cost $8.00 to fill. About 1-2 minutes to recharge the gun. It'll spoil you since all your time will be spent shooting. Stock up on pellets for that cyclone. BTW, have you had a chance to try the 18 gr. jsb's in that fine gun of yours?

kevin

 
At March 17, 2009 9:50 PM, Anonymous Volvo said...

Kevin,
Thanks for the point of reference on the size. I was a little gun shy since I found many Springers’ I owned dwarfed actual firearms in my collection.

On another note I was at the Sportsman show in Chester W VA a couple weeks ago and saw quite a few Elk mounts. Wow. They make a good size buck look like a fawn. I understand your “enough gun” stance better now. Quite a few guys from out west at the show.

One outfitter had an all inclusive deal for a bear hunt in Canada for $1100. (Excluding transportation.)
Have not tried the JSB 18’s yet but I will. Right know Kodiaks and CP are the winners.

Appreciate you for not busting me for the typos in my last two posts. Must be the cold medicine : )

 
At March 17, 2009 9:55 PM, Anonymous name said...

Forgot,

I am going to guess that most of the amateurs will not be posting tonight.

Happy St. Patrick’s Day : )

 
At March 17, 2009 10:01 PM, Blogger kevin said...

Volvo,

Kodiaks and jsb's are similar in accuracy in my gun at long range (50 yards is all I can shoot now until I get to the place in the mountains. Maybe another month or so to be able to try 100 yards). At 30-40 yards the jsb 18 gr. win hands down.

Meant to ask, Where did you get the ldc for the cyclone?

Yeah, elk are quite a challenging quarry. Most folks don't realize how much smarter and stronger they are than deer. Bear are strong but stupid in comparison and once you kill a bear what have you got? Ever eat bear? Fatty and strong tasting. The worst of both worlds. Killing something for the sake of stuffing it was partly to blame for me getting out of guiding. Disrespect for the animal in my book.

kevin

 
At March 17, 2009 10:10 PM, Anonymous Anonymous said...

BB,

This is just reporting on your advice some posts prior about keeping a interval of a minute or so when chronying a co2 rifle.

I did some tinkering on it, had a more stable bench ang chrony setup, sorted some pellets by weight and did the test yesterday. I had a stopwatch to ensure I have 60-65 seconds interval between shots.

Here is my 12 shot string result:

1 621.7 fps
2 626.2
3 627.1
4 627.2
5 625.9
6 626.5
7 627.6
8 622.3
9 626.0
10 619.1
11 616.7
12 611.2

Is this typical for a co2 rifle cal .22? Any comments on the velocity string?

Thanks.

Abe

 
At March 17, 2009 10:45 PM, Anonymous Herb said...

Volvo,

What meter did you buy?


Did a quick search for "Impulse sound meter"

Casella CEL-254 for $1200 From Fischer...
https://www1.fishersci.com/wps/portal/!ut/p/c1/04_SB8K8xLLM9MSSzPy8xBz9CP0os3iTQCdLP3MPIwN_U39TAyMvP39DZyNvQ38LM6B8pFm8n79RqJuJp6GhhZmroYGRmYeJk0-Yp4G7izEB3cGpefrhIDvxmwGSN8ABHA30_Tzyc1P1C3IjKjx1HRUB-i8U3Q!!/dl2/d1/L0lDU0lKSWdra2trIS9JSFJBQUlpQ2dBek15cXhtL1lCSkoxTkExTkk1MC04MXcvN180UUI5TjdIMjAwUjJFMDJGVFZOR1BHMzBWMi9zYS5Qb3J0bGV0TkFWQWN0aW9u/?ru=http%3A%2F%2Fprodwcsserver%3A9060%2Fwebapp%2Fwcs%2Fstores%2Fservlet%2FFisherProductDisplay&catalogId=29102&productId=647124&langId=-1&distype=2&isChemical=false&fromCat=yes&catCode=SA_SC&brCategoryId=54766&hlpi=&highlightProductsItemsFlag=&fromSearch=

http://casellausa.com/en/docs/data/cel/cel-200_series/cel-24x_brochure.pdf


So It would appear that an IMPULSE sound level meter, which is what you need for a gun shot, is fairly expensive. Not sure what other options are available.

Herb

 
At March 17, 2009 10:54 PM, Anonymous Anonymous said...

random notes:

rms is an average measure of a periodic function. It has no meaning for an impulse.

accurate peak measurements require large post detection bandwidth.

A-weighting describes perceived frequency response of detectable sound level to the ear (dBA). A pure impulse contains all frequencies. The amplitude vs time shape any particular pulse will determine its frequency content, and thus affect perceived loudness.

dB is a relative measure, it means nothing without the proper reference point

in terms of amplitude, dB=20log(ratio)

in terms of power, dB=10log(ratio)

 
At March 18, 2009 12:13 AM, Anonymous Herb said...

RE: "A pure impulse contains all frequencies."

Have to think about/research that. It doesn't seem possible to have a "pure impulse." The lower level range to the highest frequency range is quite a range. On the low frequency range the impulse would have to have quite a time duration.

Human hearing is from 20Hz and 20,000Hz. To have sound at 20 Hz would imply that the sound lasts at least on the order of 0.05 seconds. That seems much too long for the peak of a gunshot. It would seem that the muzzle report would be more of a broad band high frequency response, but that the low end would taper off. I'd also expect some "coloring" of the sound due to the length of the barrel. Kind of like many musical instruments can all play the same note, but the harmonics are different so the note sounds different on each instrument.

Oh well, as Annie said "tomorrow, tomorrow, its only a day away..." Love science. There is always something else connected to topic of study to learn...

Off to bed...

Herb

 
At March 18, 2009 7:46 AM, Blogger B.B. Pelletier said...

Abe,

Your rifle is very consistent. Most CO2 guns are. Only the cooling effect slows them down, and your minute pause is what keeps yours consistent.

B.B.

 
At March 18, 2009 9:09 AM, Anonymous Anonymous said...

B.B.,
A guy gave you the link of "Sound Intensity" in Wiki, but I think this one is better:

http://en.wikipedia.org/wiki/Loudness


Alan

 
At March 18, 2009 9:53 AM, Anonymous Anonymous said...

Herb,

Here are some of the specs from my meter:

Lo=30-100dB

Hi=60-130dB

"A" and "C" frequency weightings

Selectable - FAST 125mS, SLOW (1 sec)

Accuracy of ±1.5 dB

Weight 230g

Overload indicator

Hold: Holds readings with Max Value 3 minutes

IEC 651 Type 2 standards

Next calibration due 2-10

As you can see impulse is not an option. Cost wise it was only a couple hundred bucks.
Oh well…
Volvo

 
At March 18, 2009 11:47 AM, Anonymous Herb said...

Volvo,

Thanks for the specs on your meter.

The FAST (125mS) and SLOW (1 sec) integration times are probably too slow for impulse.

There would also seem to be a different weighting for impulse versus "A" and "C" frequency weightings. The Casella CEL-254, which is a cheap(?) impulse meter, doesn't seem to be able to display a histogram of frequency range vs. intensity.

I'll try to poke around some more and see if I can find out more about these two points.

Herb

 
At March 18, 2009 12:36 PM, Anonymous Volvo said...

Herb,
I tried changing settings and testing the HW30 \ R-7 again and found that while it displays a consistent reading for each shot it also says “over” in small letters at the bottom which means error. (Silly engineers should have made it say error and I would have noticed sooner)

Interestingly it doesn’t get an error when testing the fully factory shrouded Cyclone. Maybe a shrouded PCP lacks the sharp crack of a Springer that it can’t pick up?

Quick history – I ordered the unit at about 1:00 am out of frustration to help in deciding which rifles to keep and sell. It would of made an interesting video, me cocking my head from side to side as I listened to the various reports. Needless to say I am very un-engineer like as I tend to make decisions quickly, which usually works ok. Obvisiouly not in this case.

I finally found the sales invoice; it came from a company called D.A.S. It is unfortunately past the two week period for returns. I am going to e-mail them and see what they would recommend for our needs. After that we will have to convince Wayne to order one. I have a feeling it will be too much for my pockets.
The only issue with BB's list is that they are all Springer’s … I won’t even guess how many rifles Wayne has to test.

Volvo

 
At March 18, 2009 12:58 PM, Blogger B.B. Pelletier said...

Volvo,

No, all the guns on my list are not springers. 14 of them are PCPs, single-stroke pneumatics, multi-pump pneumatics and CO2 guns.

B.B.

 
At March 18, 2009 1:52 PM, Anonymous Volvo said...

BB,

I stand corrected - again or still. Thanks for keeping me focused. I cheated yesterday by just paging down to the list in my excitement. And clearly still haven’t taken the time to digest it. I guess I was thrown by the disparity of my numbers.

Would it be fair to say that the list is just a little dated? Of course by that I mean it just lacks all the rifles I’ve owned or wanted to know about. : )

Volvo

 
At March 18, 2009 2:09 PM, Anonymous Herb said...

Volvo,

Found some information on time constants.

"Fast corresponds to a 125 ms time constant. Slow corresponds to a 1 second time constant. Impulse has a time constant of 35 ms.

As these time constants were set in standards, they have continued in digital meters, now being calculated or simulated before being displayed, stored or used to calculate other acoustic parameters that need the time weighting."

http://www.noisemeters.com/help/faq/time-weighting.asp

NIST standards are probably the ones referenced.

Herb

 
At March 18, 2009 2:51 PM, Anonymous .22 multi-shot said...

Just catching up on the last few days.

I'm going to step out on a limb and say that you can't MEASURE the exact contribution of the various frequencies to a sound peak even though you can tell what frequencies it consists of. You might be able to calculate it.

The frequencies that make up the source don't have a constant sound level (amplitude), so the impulse/peak is a one time occurance (one wave) at a specific location. The largest impulse sound in a 3D area around the airgun can be at a distance other than zero since the amplitude is determined by the wave superposition principle.
http://www.kettering.edu/~drussell/Demos/superposition/superposition.html

I see the impulse sound meter to be like a float that will show the height of the highest wave at some location on a pond.

I am not familiar what is available with sound meters, but I tried looking for a meter that measures "peak" sound. I saw some around $200 that would do this. It also sounds like one that does "flat" weighting (not A or C) probably does no weighting.

http://www.markertek.com/Product.asp?cat=AUDIOEQUIP&subcat=AUDINT&prodclass=RACKUPS&baseitem=RU%2DSM16&search=0&off=0&showreturn=0&utm_source=&utm_medium=&utm_term=&utm_content=&utm_campaign=

http://www.tnt-audio.com/clinica/spl-meter_e.html

.22 multi-shot

 
At March 18, 2009 3:06 PM, Anonymous Herb said...

RE: Weighting / Time constant...



From:
http://www.ptpart.co.uk/show.php?contentid=70


"
...

Figure 1: A, B, C and D Weightings

...

The 'Impulse' characteristic is about four times faster than the 'Fast' response. It has a very fast rising time constant (approximately 35 milliseconds) and a very slow falling time constant. This characteristic presents a value representative of the loudness of a short duration sound, and is therefore used to determine annoyance rather than hearing damage risk.

...

For impact noise, the OSHA requires measurements to be made using a sound level meter with a linear frequency response, a peak detection circuit and a response time which is approximately 1000 times faster than the 'Impulse' response. This facility is only available on specialised impulse sound-level meters."



Herb

 
At March 18, 2009 5:28 PM, Anonymous .22 multi-shot said...

Volvo & Herb,

Thanks for the web sites!

Interesting the difference between impulse and peak. It does sound (pun intended) like impulse would be what you would want to measure for airguns.

It seems strange that meters to measure the peak sound pressure are called impulse meters!

.22 multi-shot

 
At March 18, 2009 7:16 PM, Anonymous Herb said...

RE: Impulse measurement

Trying to figure out if in fact the "standard" "impulse measurement" of 35 milliseconds is fast enough for a gunshot. Read a couple of things that make it sound iffy.

Really good lab grade instruments would be able to measure even faster evidently. Since the sound is very loud, you need a very fast peak detection circuit to get the maximum value. So basically, the faster the peak detection circuit the higher the dB readings until you get a "fast enough" meter.

With a very loud dB value such as a gunshot, even one shot would seem enough to cause damage. Wonder if Steve Lewis could be contacted and if he could shed some light on what characteristics are needed in a meter to measure gunshots accurately.

Herb

 
At March 18, 2009 7:33 PM, Anonymous .22 multi-shot said...

Herb,

The link you posted mentioned this.

"The 'Impulse' characteristic is about four times faster than the 'Fast' response. It has a very fast rising time constant (approximately 35 milliseconds) and a very slow falling time constant. This characteristic presents a value representative of the loudness of a short duration sound, and is therefore used to determine annoyance rather than hearing damage risk."

I guess what it comes down to is whether to measure the annoyance factor (so you don't annoy your neighbors) or the hearing damage factor.

.22 multi-shot

 

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