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Decibel meter testing for 5 popular rilfes (includes NC comparison)

October 2 2013 at 11:17 PM
  (Login gunnerKY)
YF12

Hello all,

I know the question about "back yard friendliness" has been asked many times on this forum.

The marauder seems to be to gold standard of quiet and its often asked how one rifle or another compares to it.

Well, just for the sake of curiosity, I bought a decibel meter to test out my arsenal.

To set the test up, I put my mete on the 60-80db scale and placed in on a tripod about 3 feet infront of the muzzle and about 45 degrees to the side. I put it on min / max and took the highest reading of 5 shots. Shots were fired from inside the basement to a target in the back yard so while the numbers might be inflated slightly due to the enclosed area, the comparisons should still be valid.

Here are the results...

.22 Marauder.....73.6db
.22 FX Royale (with Huggett LDC).....75.4
.22 Daystate Huntsman Classic (with Huggett shroud).....75.7db
.25 Cricket with original shroud.....88.5db
.25 Cricket with NC shroud.....75.6db!!!
.22 Beeman R9 springer.....88.6db
.17 TX200.....80.3

As suspected, the Mrod is in fact the quietest rifle, but what blew my mind is the NC shroud for my Cricket .25. It brought the sound down to the same level as the smaller caliber .22 FX and Daystates WITH the high performance Huggett systems! That Cricket shoots over 50FPE too!

In my opinion, anything registering in the 70's are very back yard friendly. My TX200 is borderline and the R9 is on the high side depending on your neighbors.

Well, hope this helps for some of your future purchases!

Take care,

Brian



 
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AuthorReply


(Login thegr8wendt)
YF

What kind of DB meter did you use?

October 2 2013, 11:23 PM 

I tried doing the same thing with my smart phone & a free app. Didn't work so well in the wind. I ran out of time but my next effort was to move it inside for more controlled results.

Thx for doing this!

~MW~

 
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(Login MikeSSS)
YF12

Superb information, very valuable, thanks. nt

October 2 2013, 11:31 PM 


 
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(Login itsmekeoni)
YF

Good post but what was the reading for ambient noise where you were testing? nt

October 2 2013, 11:35 PM 



-Keoni

====================================================

 
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(Login neilclague)
YF

It would not register ambient background levels

October 2 2013, 11:53 PM 

Keoni if you look at his settings it is very unlikely the ambient background noise would register on the meter. Some meters have to be set for a range that you think the sound will be in, say 60 to 80dbs and anything below that does not register, anything above that will show some kind of message that the range needs to be increased. I had a meter like that a long time ago and gave it away and bought a decent one, Neil.

 
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(Login itsmekeoni)
YF

Is that how it works?

October 3 2013, 12:22 AM 

The only meter I ever tried would register ambient noise and then the noise from the airgun on top of the ambient noise. Thanks for clearing that up Neil!

-Keoni

====================================================

 
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(Login neilclague)
YF

Not all of them do

October 3 2013, 12:28 AM 

Some meters have a range from 30 to 120 but that varies for meter to meter and there again there is the meter as used in this test that has to be set for a certain range, say 40 to 60 or 60 to 80 and they only register numbers between those figures. My meter registers from very low background noise up to about 130dbs, not totally sure on the max as I have never managed to get that high. I think the highest I managed to peak at was 110dbs. All the best, Neil.

 
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Martin Orro
(Login morrodds)
YC

dB meters

October 3 2013, 12:59 AM 

Greetings Neil,

I'm ignorant as to the different types of dB meters. I understand a bit about frequency weighting filters, but am unsure as to which type to use in the context of airgun noise levels.

Is there a preferred type of meter to do these types of comparisons?

Thanx, Martin

'It used to be only death and taxes; now, of course, there's shipping and handling, too.'

 
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(Login neilclague)
YF

I do not even bother with them

October 3 2013, 1:33 AM 

I do not base anything on db readings of db meters, my goal is to make shrouds and LDC's for guns so that they are easy on the ears and enable shooters to shoot at home without upsetting the neighbors. If you have a gun that is very quiet what does it matter how many dbs it makes? I know from experience that the human ear detects things differently and to some shooters the only way to find out what is actually quietest is to use a meter. But I still say what does it matter, if shroud 1 measures 85 dbs and shroud 2 measures 75dbs but shroud 1 sounds quieter to my ears I am going to use shroud 1 so what is the real point of knowing how many dbs a report is. Plus readings vary so much from meter to meter and varying conditions what is the real number to use as a baseline for what is acceptable? If you feel the need to get one I would suggest getting a mid range one, not the cheapest and not the most expensive, just one that will give consistent results and not vary from shot to shot. You should be able to pick up a fairly reasonable one for about $85, I know there will be those who argue against that, but I would not buy one of the $30 models, I have given away several of them, they are not worth wasting your money on, Neil.

 
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(Login morrodds)
YC

Thanx

October 3 2013, 1:51 AM 

My interest is in comparing the various airguns I have made and purchased. Many people inquire as to the noise level of my replicas and I don't have a good answer. Since I have several PCP, CO2 and springer rifles it might be interesting to compare them to 200+ year old tech.

Martin

'It used to be only death and taxes; now, of course, there's shipping and handling, too.'

 
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(Login neilclague)
YF

If you need one e-mail me

October 3 2013, 1:54 AM 

Martin if you would like to use mine for a while for testing I am ok with letting you use it for a month or so. I do not want to get rid of it as it does come in handy once in a while when my ears do not tell me what I need to know, Neil.

 
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Doug
(Login dyotat100)
YF12

Re: Decibel meter testing for 5 popular rilfes (includes NC comparison)

October 2 2013, 11:48 PM 

The only way it is comparable is if they are same caliber and shooting same fps. With power comes noise.

 
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Doug
(Login dyotat100)
YF12

Re: Decibel meter testing for 5 popular rilfes (includes NC comparison)

October 2 2013, 11:48 PM 

The only way it is comparable is if they are same caliber and shooting same fps. With power comes noise.

 
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(Login neilclague)
YF

He mentioned that in his post

October 3 2013, 12:00 AM 

If you read his post he said he was surprised by my shroud bringing his 25 caliber Cricket down to the levels of his smaller caliber guns. He is not trying to make direct comparisons he is just making a statement, why are people ready to criticize posters who are just trying to give out results of tests they have made, he is just posting results he got from various guns, no detailed analysis or trying to make direct comparisons, just a few simple DB numbers, why can't it just be taken for what it is worth. I do not think any of us set up laboratories and do scientific testing of them!

 
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(Login dyotat100)
YF12

Re: He mentioned that in his post

October 3 2013, 12:59 AM 

Not trying to criticize.

I'm just saying that fps makes a big difference in sound out put.

What fps is each gun shooting at?

I can turn my .25 or .257 down to 800 fps and be quieter than anything out there.

I have spent sometime building different shroud setups and experimenting with my condors to come up with what I have.

 
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(Login neilclague)
YF

Purpose of a shroud

October 3 2013, 1:22 AM 

Doug if you are going to turn a guns power down to achieve a quiet report then there is no real need for a shroud, the idea of a shroud is to be able to use the gun at full power or a high power for hunting or whatever without upsetting neighbors or doing damage to the ears of yourself and others. I would not expect the person who posted the results would turn the 25 caliber Cricket down to a lower power than the other guns to try and post favorable results, the object of his post was to show how various shrouds worked compared to others, the fact that they are on different guns with different calibers really does not prove anything in the real world other than the Cricket with my shroud on was comparable to the smaller caliber guns with other makers shrouds on them. The only real way to do a direct comparison is to put them on the same guns shooting at the same velocity and power. But that was not what the tester was trying to do, he was just posting some informative figures to let other shooters get some idea of what to expect from different guns. We can all turn our guns power down to achieve a quiet report but what we are trying to show is that you can use guns on full power with an effective shroud on them, without having to alter the power of them. Neil.

 
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(Login itsmekeoni)
YF

"With power comes noise", true but...

October 3 2013, 12:20 AM 

...isn't it something when a larger more powerful airguns is quieter? I agree with Neil this wasn't supposed to be a scientific test and there isn't much reason for one. It would be nice to see a Marauder compared in all calibers against each other, my money is on the .177 being louder than the .22!

-Keoni

====================================================

 
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sactargetshooter
(Login sactargetshooter)
YF

Thanks for the information!

October 3 2013, 12:58 AM 

That is good information to have. If each of us do our part and post our results, we will soon have a good database. The nice part of the dB scale is that it is not distance sensitive. Let's say I collect my data from my guns, but I place the meter 5 feet from muzzle, the relative differences is still valid. If a gun is 3dB more quiet than another gun, it is 3dB more quiet regardless of distance to sound meter.

NC products are worth every penny. 3dB is about doubling. This means in linear scale, the NC shroud reduces the sound of your .25 Cricket to 1/(2*2*2*2)=1/16 compared to the original shroud! I observe about the same kind of differences with my guns with NC products.

 
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Daniele
(Login Daniele5)
YF12

Thank you

October 3 2013, 2:07 AM 

Interesting post.
I didn't know pcps were so quite compare to springers.

 
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(Login neilclague)
YF

They are not unless they have a shroud or LDC on them/ NT

October 3 2013, 2:15 AM 


 
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Hanut
(Login Hanut)
YF

Follow-up re-test advisable

October 3 2013, 3:11 AM 

Those bringing up the point that the test wasn't valid get criticized. They simply want someone to explain, exactly, how this information is useful. What is exactly the useful information. A lot of us don't see it:

The test doesn't follow the rule of "all things held constant". The tester gives no disclaimer that the "test" was non-scientific, though it's obvious. And the "test" asserts to proving "backyard friendliness"-- loudness; it was not asserted to be a mere "statement". It would be misleading for a gun in the group to be set at 12-lb energy, while another is set to 30- or 50-lbs energy, and then claim the 12-pound-shooting gun is inherently more backyard friendly.

And the "tester" IS making direct comparisons among the guns "tested". With all due respect to the tester-- but not so much of it due to complaints of "Why can't it just be taken [the test] for what it is worth?"-- It is being taken for what it's worth. For many here, who aren't bothering to post, for less worth than what some here are granting.

And there IS a reason for a "scientific" test-- to give it maximum, reliable, worth, and thus usefulness in what the tester calls "future purchases". It doesn't take a laboratory to do a test, just the same equipment used here and matching guns as to caliber and, literally, comparable settings. That would just require a little bit more meticulousness.

As for the those "[grateful] for the information", it really can't be determined what useful information they came away with. It would be interesting to know what the "useful information" will actually be used for. As for the statement that the Marauder is the "gold standard", many airgun owners no doubt missed the awards ceremony and didn't know that. When that claim is verified, that might have some usefulness.

This is the useful information one can gather: if one were to have each of the guns used in this "statement" (which looked more like a description of a "test")-- with same individual calibers, fill-levels, power settings, etc.-- some guns will result quieter or louder than others. But you have to have the same identical guns just to duplicate near the results. And the same settings and calibers at the moment of testing. Can one really rely on this sort of "test" as useful for "future purchases" of the a "backyard friendly" gun, as the tester hopes for readers of the post?... You can't.

The test isn't reliable or useful, and the comparisons are not valid as stated.

This is only to question the stated purpose of the test, which was to provide useful information. And to support others suggestions that a few more "things be held constant" in a follow-up re-test.

 
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Grady
(Login luckybones47)
YF

Well said Spock! n/t

October 3 2013, 3:33 AM 



grady

 
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(Login neilclague)
YF

Geeze what is wrong with you

October 3 2013, 1:20 PM 

The guy is simply posting a few simple results for others to see what type of DB ratings he was getting from his various guns, he never made any claims they were scientific or accurate, People do this for fun and to give others an idea of how different guns relate to each other in their report, yuor post is ludicrous and uncalled for, you need to step back and think before you make a post like this, some of us enjoy air rifles and don't give a dam about scientific results! How many times have members posted asking for db ratings of various guns, and how many have stated that they are not all dead accurate but as long as the same meter and conditions are applied for all of the guns it gives a fair indication of how the guns compare to each other, just give the guy a break and quit ball breaking.

 
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(Login thegr8wendt)
YF

I agree with Neil...your response in ridiculous

October 3 2013, 6:43 PM 

This is an unscientific test. And for those who have those guns it provides a good idea of the actual DB level. Obvious Brian tested the guns he has in his collection or readily available, he doesn't work at an air gun shop where he has access to numerous guns of all the same FPE and caliber.

If other people (or manufacturers) would do the same (under the same conditions) then we could actually start a spreadsheet or database with the average noise levels.

Again, many thanks to Brian for attempting to capture some of the noise readings.

~MW~

 
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ChrisLJ
(Login Pb82Air)
YF12

Thanks Brian

October 3 2013, 6:04 AM 

Thanks for taking the time to post your findings. Unfortunately, there appear to be a lot of scientists here with a PhD in physics who don't approve of your methodology. Apparently it doesn't pay to do a little backyard comparison and share the results here in an informal and friendly manner. I guess if you ever decide to post again you should state the disclaimer that you are not Stephen Hawking so as not to confuse the rude and anal.

 
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(Login rtoler45)
YF

Too Funny ...

October 3 2013, 10:57 PM 

Appreciate the humor.... And I think you are right... LOL

 
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daveshoot
(Login daveshoot)
YC

It's a good test, and there WAS a constant

October 3 2013, 8:31 AM 

The location of the meter was the constant.

Under the shooter's circumstances, one gun is "quieter" than another in decibels, period. It doesn't matter how many fpe or what size bore. The report, as measured from a constant location, is measurably louder or quieter relative to the other guns in the test. That is all.

To someone concerned about backyard friendliness, it would be instructive. Actually this test measured "basement friendliness" since it was in a closed space with some reflections.

Valid criticism is part of almost any test result. But, before splitting the hair too finely, consider that if all you want to know is whether a potential purchase might annoy sensitive neighbors, and you already have one that doesn't (or does), the information would be useful. If I already owned, or had heard, one of the guns in the test, and was considering another gun mentioned in the test, this would still be a useful comparison.

What the test does not capture (nor would it be reasonable to expect it to) is some of the other differences in sound, like frequency and duration. Two guns producing the same decibel level aren't necessarily perceived as equally loud by a human ear. The frequency range and its harmonics, as well as the duration of the peak sound level and the speed at which the sound gets to peak, have a lot to do with how loud or annoying we think a sound is.

For this the test would need a spectrum analyzer, which would be fun, but expensive.

Also, a decibel database that was crowd-sourced would probably not be useful. There really would be too many variables in placement and meters to state that a certain gun has an absolute db value of x. Within any given session, the comparisons are relative, but useful based on that alone.

Thanks for the post, Brian!

 
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Mike
(Login Mike17670)
YF

Your findings on the springers.

October 3 2013, 8:43 AM 

You are very close to what I have found to be true with my own test on my springers. I also found that with out the baffle systems installed they do tend to be a bet nosier , roughly 10 db.

Good post!

Mike

 
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(Login gunnerKY)
YF12

"re-test advisable"...LOL, I'll get right on that...

October 3 2013, 9:33 AM 

Must say Im surprised by the number of people unsatisfied with this information.

Im an engineer by degree and trade and am very familiar with the principles of scientific testing.

Those arguing that these results are not a full on experiment with variable control are correct.

Im not sure I see where I made that promise or statement though.

Anyone arguing that there is "no value" in this data are simply wrong. The "value" just needs to be taken at face value for how the test was conducted.

If you have questions about FPE, etc....just ask! All of the PCPs are shooting within 50FPS of eachother and are representative of the "tune" as received by the manufacturer.

That said, its easy to see the Mrod is very quiet. The Cricket is louder than an un shrouded springer with the factory shroud, and quiet as a smaller caliber air rifle with a Huggett shroud with NC's product installed. I think thats VERY valuable information. Especially for anyone interested in these new very popular Cricket rifles. It also gives them some quantitative numbers to consider if they are looking to upgrade with a NC product.

The fact that Ive been "encouraged to re-test" is hilarious. I acquired the info "I" needed from my own testing and only posted this to give back to the forum as an active member and content contributer. For the right price, I'll conduct any test you want in a scientific method complete with full report out. You might not want to pay that salary though.

So as stated before, take this at face value. Ask any questions you like in a respectful manner, but be careful with "how" you criticize. You dont want to discourage other members from "contributing" good content just because they may not have the ability or desire to dedicate the time and skill reqired to meet your personal expectations.

Thanks to those that posted positive comments in reply.

Take care!

Brian


 
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(Login shooter78)
YC

+1

October 3 2013, 9:58 AM 

I found it quite interesting!

 
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(Login btango05)
YF12

Thank you, I hope this doesn't discourage you from further

October 3 2013, 10:07 AM 

Tests and postings of your findings in regards to airguns. I read your post last night and meant to reply with a thank you, but found it late in my break and didn't have time. I found it very useful and wish it had been available when I was deciding on which PCP to get. I have a Daystate AW .22 w/Huggett and a Cricket .22 with factory shroud. I shoot in my back yard and I haven't had any complaints so far. I've been contemplating on getting a NC for my Cricket, but even Neil says it's a quiet gun by itself. I still wouldn't mind "blinging" it up when I have some extra $ to throw around with his carbon fiber shroud happy.gif

Anyhow, thanks again for your data.

 
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TexasSteve
(Login LTLurker)
YF

+2

October 3 2013, 10:07 AM 

good for mew too.

I do the neighbor test, if the neighbor looks out the door after I shoot, the gun fails the test. All have passed so far except for my USFT.

 
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Rob
(Login EMrider)
YF

Predictable....

October 3 2013, 12:56 PM 

Any post on sound testing generates a predictable rebuttal from the professor poindexters of this world about how the results are not reliable, comparable, etc.....

I don't think you were submitting this info to a peer review journal. Just sharing FWIW. For my purposes, it is plenty and useful.

Thx
R

 
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(Login Arkmaker)
YF

Yep Brian, I sure found it useful! Thank you for posting...........n/t

October 3 2013, 9:15 PM 


 
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Birdo
(Login Birdo22)
YF12

It's good post.

October 3 2013, 11:41 AM 

But it doesn't address how the noise is perceived by people. THe springers are supposedly louder according to the results, but they make a mechanical noise that people don't associate with a gun.

The PCP's and Co2 make a more distictive sound gun like noise.

Don't try to draw too many conclusions from this testing.

 
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(Login neilclague)
YF

Noise is noise no matter what makes it

October 3 2013, 1:30 PM 

If the meter can pick up noise 3 or 5 feet away from the muzzle then the shooter will hear the same noise so if a meter picks up the mechanical noise then so will the shooter. Springers can quite easily have a louder report than a PCP with a good shroud or LDC on it. I have several springers that are much louder than my own Pneumas with LDC's on them and the Pneuma is known to be a loud airgun without anything on it so his test is valid for PCPs and springers. People can draw their own conclusions and I am sure do not need any help on that. I see some have already made some rather weird conclusions and think they are the type of air gun shooter who does it for scientific reasons and not for the fun most of us use them. I enjoy the hobby and just do not get the people who constantly berate others for making a fun post to share with us ,I enjoy this hobby/ sport, why can't you all just enjoy the guns and if you don't like what someone posts when he wants to share with us just move on and find a post that you do like. I thank the poster for sharing his results with us and hope the small minded members do not stop him from wanting to post again, thanks for the post Brian I am sure a lot of us enjoyed seeing the results you posted, Neil.

 
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Birdo
(Login Birdo22)
YF12

Not true

October 3 2013, 2:28 PM 

Noises sound different all the time. I can tell the difference between a chain saw and a hot rod, but they are both loud.

I don't think springers sound like powder burners, but that's just me. I shoot them all, so I don't have an axe to grind.

 
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(Login neilclague)
YF

yes it is true

October 3 2013, 4:28 PM 

That is why people actually use db meters to determine actual noise levels, just because a chainsaw sounds different to an air gun does not mean it is louder, you can only tell what is going to actually damage your hearing by using scientific equipment. When they test factories they test them in different areas and take readings to see where ear damage will occur, you can hear a chainsaw from 100 yards away and it will not damage your hearing, but bring it to arms length and that is a totally different story, you need to know your facts before you say something is not true! You can call something inaccurate but calling something not true indicates an intention to deceive or lie! Just because noises sound different does not make it louder, noise is noise so when you take a db reading it measures actual noise and not what you think you hear!

 
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birdo
(Login Birdo22)
YF12

thats true

October 3 2013, 5:05 PM 

Somethings are louder than other things, and somethings sound different than other things.

Decibel meters only measure sound pressure level, they can't tell the difference between bethoven and acdc.

I think Brian had fun testing his rifles and did a good job. My quietest is a talon ss with the new soundlok kit. The s510 is a bit louder, tho neighborhood friendly.

 
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Vance Purdy
(Login Vance-001)
YF12

Info from an earlier discussion

October 3 2013, 4:39 PM 

Back in September there was a similar discussion about measuring airgun loudness.

http://www.network54.com/Forum/79537/message/1378340429/Info+about+sound

with a lot of useful comments.

Seems it requires a very specialized meter to capture the true peak sound level. However, I suspect that commercial ones can give useful relative measurements. Thanks for the info, Brian.

 
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(Login neilclague)
YF

If the meter has a fast response time it should give good results

October 3 2013, 4:48 PM 

There are way too many settings and factors to take into account but a meter with a fast response time and able to capture the maximum level it should give a fairly close reading. I have a very expensive industrial unit and a mid level meter that also has fast response times and they give very similar readings. I have tried the cheaper $30 to $60 meters and they were way off what the 2 other meters gave me so i ended up just giving them away. I don't know why so much emphasis is put on db readings by some members, surely all that is really important is does the gun sound quiet enough for you and does it upset the neighbors. If the gun sounds quiet enough for your ears and it does not bother the neighbors who really cares what dbs it makes? But those are my personal feelings and i know there are some who are anal about db numbers, I just refuse to get caught up with them and do not disclose any numbers for anything I make, they are quiet and that is all I will say so anyone wanting numbers will have to do their own tests!

 
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(Login bubba9)
YF12

Testing

October 3 2013, 9:04 PM 

Brian, Thanks for testing your Air Rifles and reporting the results, as a new person to the sport I appreciate all information that I can get relative to neighbor friendly shooting.

I first purchased a Weihrauch HW95 and was told at the time of purchase that I probably wouldn't need a moderator. I shoot it with no complaints from the neighbors (two of them are police officers that know I shoot and are not concerned). I wanted to buy a PCP Air Rifle and agonized about quality, accuracy, weight, etc but - mostly noise. I got a lot of input from members of the forum and I purchased a FX400 Royale 22caliber. Your information confirms that I was in the ballpark as far as relative noise is concerned and I'm very pleased with my purchase and with your posting.

Thanks, Jack

 
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sactargetshooter
(Login sactargetshooter)
YF

Sound clips

October 3 2013, 9:43 PM 

Maybe it'll be helpful to record and post sound clips in such tests. As long as the mic is a good one, the gain is fixed, and the amplitude is not clipping, a sound clip can provide a wealth of information. Sound clips of different guns firing in the same condition can be used for infotainment purposes.

I'll probably do just that this Saturday.

A sound clip eliminates unknown factors of sound meters (like response time and etc.). It can also take care of the background noise issue. A program like Audacity can analyze the signal to noise ratio between parts of a clip. Or, you can write your very own signal analysis program to analyze the clip.

Brian, thanks for your enthusiasm and sharing your data. Now I want to do my own tests and post my own data!

 
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daveshoot
(Login daveshoot)
YC

AND another thing...

October 3 2013, 9:47 PM 

In the most instructive test of all, there were two constants:

Meter and placement (lumping that into one), and:

.25 Cricket with original shroud.....88.5db
.25 Cricket with NC shroud.....75.6db!!!

Before we eschew numbers completely, let's recognize that a 10 db drop is perceived as half as loud by most humans. You might argue with that, but Brian's test shows a very significant reduction with the addition of a shroud of a particular brand.

If you had a potentially annoying airgun and wondered whether the investment in said NC shroud was worthwhile, this too would be instructive. It is not just a bada$$ bling accessory, like a spoiler on a 55 mph sedan, but an effective solution to a problem.

So, without being a numbers freak, we still have some useful performance data re: does the thing work? Apparently, it does.

 
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sactargetshooter
(Login sactargetshooter)
YF

3dB is 2x

October 4 2013, 1:11 AM 

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

Our hearing is logarithmic and not linear. That means we feel 1x to 2x is the same amount of increase as 2x to 4x, 4x to 8x and so on. That is partially why signal to noise ratio is expressed in a logarithmic scale.

Whether 10dB feels like 2x is important when we actually need to process the numbers. Doubling distance reduces S/N ratio to 1/4, which is roughly -6dB. This means a gun that is rated at 82dB sounds like a gun that is rated at 76dB but at twice the distance because 82dB - 6dB = 76dB.

In the case of the NC device, the reduction is >12dB. This means a gun with the device sounds like a gun without but at 4x the distance. A .25 Cricket with NC device at 10 yards sounds like a .25 Cricket without NC device at 40 yards in terms of signal to noise ratio.

Of course, an NC device also changes the distribution of frequencies as well as the sharpness of amplitude change, and a sound meter does not quantify those. This means that to a human ear, the effectiveness of an NC device may be more (or less) than -12dB.

 
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ronald toler
(Login rtoler45)
YF

Tnx for INFO nt

October 3 2013, 10:55 PM 

.

 
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(Login BuckoFama)
YF12

Way to go Brian! Your gonna get the forum shutdown, like our government ! Nt.

October 4 2013, 7:08 PM 


 
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