"N2 is quieter?" testing

[Magluvr]

I just got a dB meter from my friend and am going to do some experimenting to prove or disprove that n2 is quieter than co2. However, before I start I was wondering if I need to modify any of my testing procedures to get a "more fair" result.

I am going to take the marker ~100ft from any building to help cut down on echoes. I am then going to set up a tripod to hold the gun steady, and about 2ft away I'm going to mount the dB meter to another tripod at approximately the same height, with the microphone pointed towards the marker. I am then going to measure the peak dB's of the gun shooting on n2 and co2. yadda, yadda, yadda...

[Crimson_Turkey]

Make sure the velocity is the same.

[Redkey]

I wouldn't worry about echos... the rebounding sound won't be as loud as the original report... assuming you are just measuring the Max dB level.

if you can, record the velocity with each sound reading to see if they are related to each other. You might also want to try different barrels to see if that makes a difference. It might also be interesting to see how the sound levels vary with location. perhaps the N2 is louder in one spot while the CO2 is louder in another.

The more data you can collect the better... Were I doing the tests I would try and gather at least 15 measurements at each test condition.

Better yet... run it this way...

10 shots HPA
10 shots CO2
10 shots HPA
10 shots CO2
10 shots HPA
10 shots CO2

just make sure you record which shot was taken when. That way you'll be able to tell if there is any drift in the measurement system.

Also, I would try and take all the measurements at the same time so that the enviromental conditions are nearly the same for each test run.

[Magluvr]

If you have any questions, feel free to post them.

The marker I was using was:
H/L MiniMag
LX
Male Palmer Stabilizer
9 oz. CO2
3A 71/4.5k Nitro system
NO elbow, or hopper

dB's @ fps

The first barrel to be tested was the stock MiniMag barrel.
On CO2: On N2:
98.3 @ 284 98.5 @ 295
98.3 @ 289 98.3 @ 296
98.3 @ 299 98.0 @ 296
98.1 @ 297 98.4 @ 292
98.0 @ 288 98.1 @ 288
98.1 @ 295 97.5 @ 298
98.6 @ 283 98.0 @ 300
98.5 @ 295 98.0 @ 297
98.6 @ 286 97.8 @ 293
98.0 @ 294 98.0 @ 290

Averages:
98.28 @ 291.0 98.06 @ 294.5

The second barrel was a 12" Taso Winforce.
On CO2: On N2:
94.2 @ 287 95.7 @ 301
95.1 @ 309 95.7 @ 304
95.5 @ 316 95.0 @ 313
95.8 @ 307 95.7 @ 308
95.3 @ 308 95.0 @ 306
96.0 @ 298 95.2 @ 304
95.7 @ 299 95.1 @ 307
94.1 @ 291 95.0 @ 303
95.5 @ 307 96.1 @ 271
95.8 @ 302 96.0 @ 284

Averages:
95.3 @ 302.4 95.45 @ 300.1

The third barrel was a 14" Smart Parts All American.
On CO2: On N2:
95.1 @ 308 96.6 @ 272
96.4 @ 310 96.2 @ 310
94.9 @ 313 96.3 @ 311
95.6 @ 303 96.3 @ 283
95.4 @ 306 96.4 @ 306
95.6 @ 310 96.6 @ 307
95.1 @ 304 96.3 @ 301
95.8 @ 286 96.5 @ 289
95.5 @ 305 96.5 @ 309
95.3 @ 310 96.4 @ 313

Averages:
95.47 @ 305.5 96.4 @ 300.1

[Redkey]

So what are your conclusions?

and how long is a stock minimag barrel?

[Magluvr]

Sorry

I couldn't post them yesterday, so I guess I will say today...

I think that N2 is at the same sound level as CO2. You probably can't see that as well, but I believe it is since the paintballs I was using were all "odd balls". If I had spent the extra money and bought good paintballs before I performed the test I think that the results would have been a little closer matched.

Also the sound volume is all relative to the amount of force put behind the ball (that potential energy of the gas stored in the dump chamber). When you immediately switch from CO2 to N2 with no adjustments the N2 is quieter, however with the N2 the ball is leaving the barrel at a slower velocity. Once the velocity has been generally matched the sound volume also seems to be generally matched.

NOTE: the N2 and CO2 show about the same inconsistancy ratings because (A) my stabilizer wasn't at a high enough pressure -I forgot about that until I had finished the test- and (B) the paintballs were on the piddling side of pathetic. (I do know this to be a fact because on previous chronographing when using good paint and stabilizer set up properly I have record my gun with both CO2 and N2 to be within a +/-1 fps over a span of 15 shots.)

Then when looking at the averages the CO2 seems to be lower, but that is because the balls for each test were drawn randomly and some of them fit the barrel a bit better and are shown as having the higher velocity.

This brings me to the idea that the "better" the ball seals with the barrel it will both be quieter and faster.

NOTE: Some of the sound levels are quieter and also slower, I would attribute this to the improperly set up stabilizer, it wasn't feeding the valve a high enough pressure and that lowered the AIR valve's psi, which lowered the velocity... (look above about the relativity theory)

Any more questions; please feel free.

P.S. The MiniMag barrel is 8" with no porting.

[Magluvr]

Oh, if it doesn't rain this friday/weekend, I will also do a test of if the sounds from CO2 and N2 carry any differently -since the marker does sound different with the different gasses. Do you think that this could be properly carried out with just one barrel? Do you think different barrels volumes will carry differently? At what distance intervals should I move the dB meter? (I had it ~1.5 ft from the marker in the previous tests.)

[Alphawolf]

It would be nice to get dB readings >20 feet away, around playing distance, since what matters is what the opponents hear. Also, readings from behind the gun would be interesting in general. (this really doesnt have much to do with the original issue of N2 vs CO2, but since you have it all set up, why not?) This would be a good test of barrel quietness. I was suprised to see that the all american wasnt any quieter, i was under the impression that they were quiet barrels. I use a 14" Dye aluminum on my classic. Wish you could test one of those for me

[athomas]

Its always nice to see someone doing actual measured tests to prove or disprove what many believe to be truth or not.

Good job.

A note: The human ear requires a 3db increase or decrease in sound level to be able to recognise a change in volume. That being said, it looks like the data presented thus far shows no difference in audible perception between gases used.

[AGD]

Real data, NICE!!! Now you just ruined my idea :( I thought you might be able to see if a gun is shooting up on the field from the DB readings but I can see from the data that a 20 fps difference would hardly be detectable.

Got to love real testing, you get right to the heart of the matter either good or bad.

Thanks

AGD

[Magluvr]

Here is some more data taken only from the All American though. This time I did have "good" paint it was Draxxus Dusk, but it still is a bit tiny so the consistency again doesn't show. The stabilizer was turned up all the way, but I still got sporadic velocities so I have no clue about whats going on with the nitro.

With the dB meter at 10ft.
On CO2: On N2:
84.4@296 85.2@278
84.0@292 85.8@274
93.9@302 85.5@264
84.2@306 85.6@258
84.3@311 85.0@282

Average:
[email protected] [email protected]

With the dB meter at 20ft.
On CO2: On N2:
77.7@290 79.1@261
77.0@297 78.7@278
77.2@305 78.5@269
77.1@287 77.8@295
77.0@300 79.5@260

Average:
[email protected] [email protected]

If the previous "sound relativity" statement holds true then theoretically the N2 should be even louder since as you can tell it was shooting a bit slower, however I don't believe it would be a significant diffference. (I think it would be around a .3-.9 dB increase, which as athomas pointed out is an inaudible difference.

So, from all this info I would still say that for all persons' concerns CO2 and N2 are at the same sound level, bot for those that want to know the precise difference then I would say that in all actuality CO2 is a smidgeon quieter.

[Natural Newbie]

Ok, C02 is a bit quieter, but why ? Would it have something to do with the density of the gas, or expansion rate?

[Magluvr]

I actually honestly have absolutely no clue why CO2 is quieter. That is something that someone smarter than me will have to tell you.
If anybody has any ideas why please post them.

[athomas]

CO2 is quieter because it is a more dense gas. At a given pressure when compared to air, there would be more molecules of CO2 in a given area than there would be molecules of air (air is a combination or gases). More molecules means more energy is exerted on any given area at any given time.

The CO2 being a more dense gas means less pressure is required to do the same work. Less pressure translates into less of an audible blast as the gas is released. There isn't much difference in the density so the pressure differences are minor and the resulting audible differences are also minor.

[TRIAD]

The "particle density" of all gases is essentially the same. This means that no matter what gas you're dealing with, given the same size container and the same temperature and pressure, you will have the same number of particles of gas. This is why a conversion factor of 22.4 liters of gas to one mole of gas (assuming room temperature and atmospheric pressure) can be employed. The distance between the molecules of gas is so great relative to the size of the individual particles that particle size becomes negligible. So, whether I have a liter of N2 or a liter of F or a liter of Ar, the number of particles in the same size container at the same temperature and pressure will ALWAYS be the same.

As I posted in "Weight of Compressed Air" thread.

There is a difference between density of a gas, and the "particle density" of a gas. The density of different gases will of course be different, but as I posted in "weight of compressed air":

At any given temperature, all substances have the same average KE (temperature being a relative measure of the average kinetic energy of a substance). Thus, while one gas molecule might be more massive (let's compare a molecule of Ar to a molecule of N2), the one that is more massive will also be traveling at a lower velocity. (KE=(1/2)M Vsquared).
So, a mole of Ar gas and a mole of N2 gas will have (essentially) the same kinetic energy (considering they have the same average kinetic energy, and you have a specific amount of each). When you fill a tank wwith Ar, since Ar has a molecular mass of 18, the molecules have, on average, a higher velocity than molecules of molecular nitrogen (molecular mass of 28.0134). Molecular weight is therefore a moot point when dealing with the propulsion of a paintball (as far as I can see), because the average KE of each molecule of gas is still the same.

Density of the gas is therefore irrelevant from a propulsion point of view (barring any physics, of which I am ignorant).

athomas:

"At a given pressure when compared to air, there would be more molecules of CO2 in a given area than there would be molecules of air (air is a combination or gases). More molecules means more energy is exerted on any given area at any given time.

The CO2 being a more dense gas means less pressure is required to do the same work. Less pressure translates into less of an audible blast as the gas is released. There isn't much difference in the density so the pressure differences are minor and the resulting audible differences are also minor."

This is wrong. My two arguments above pretty much shows this, so I won't go into it. I'm sorry to be so blatant, but I don't want people getting the wrong idea here.