GTA
All Springer/NP/PCP Air Gun Discussion General => Air Gun Gate => Topic started by: oldpro on August 08, 2020, 01:33:31 PM
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The standard why of measuring the report of and air rifle is using a meter and capturing the Db level, this system is very flawed and really tells the customer very little. Db meters you can buy really have a wide range and back groud noise and where the meter is located can have wide effects in readings, also most people have no idea what 1 dB is and how it effects what you can hear. I want to start a industry standard using a scale based on known noise levels and then scale that 1 to 10 what do you all think? Like for example 1 being a whisper 3 a hand clap 7 a door slam 10 a shot gun...something like that
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This is a great idea and would be very helpful for us shooters that need to be stealthy (for me it is being respectful to my neighbors). How can the sound levels or comparisons be quantitated?
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Here are a few examples to start with...
http://www.straightshooters.com/decibel-ranking-of-airguns.html (http://www.straightshooters.com/decibel-ranking-of-airguns.html)
Check out the chart they have listed.
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There is MUZZLE noise ... then there is MECHANICAL noise. Any established methodology will need to take this into account being not all folks shoot the same type propulsion of air gun.
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Here are a few examples to start with...
http://www.straightshooters.com/decibel-ranking-of-airguns.html (http://www.straightshooters.com/decibel-ranking-of-airguns.html)
Check out the chart they have listed.
Good information
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There is MUZZLE noise ... then there is MECHANICAL noise. Any established methodology will need to take this into account being not all folks shoot the same type propulsion of air gun.
I agree 100%
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couple of things...
noise and sound levels are always subjecitve
my form one can in .22 LR is 2 -3 dB louder than most of my .22 LDCS but its tone makes it SEEM quieter on the same airgun.
There should be a universally accepted setup for where the meter is in relation to the muzzle. IMO there shouid also be a an accepted report structure so its an apples to apples comparision. Or at least you’re aware of how it was testes versus how you tested. ie, was it inside, in the garage or the living room. AT my shop there;s a field on one end of the building, and a building straight across. Testing in the field gives different numbers than in between the buildings
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Way to many variables to accurately quantify in my opinion.(I could be wrong)
Will be interesting to see what you come up with! Good luck.
Want to try a experiment?
Have 25 people download DB meter on their cell phone and record the DB reading of a single hand clap. Then pm you with the number. I think that will give you an idea of what you are up against.
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discussion is good.
out of it will come more good ideas
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I wonder if there are any sound engineers or product engineers on the forum. I'm thinking they would have some really good input.
Things I think would be important would be to isolate the sound to be only the sound from the product (airgun) being tested. This means the testing would have to be done in a room with acoustic tiles on all surfaces. Standards would have to be written for the testing. You'd have to decide what you are going to measure. I think you could measure how loud the sound was (dB), pitch (frequencies measured) how long it lasted (s), and how much sound there was (area under the curve, but I'm not sure what units would be appropriate).
The quality of the sound is probably just as important when it comes to irritating the neighbors but I don't think that can be quantified so I think any information regarding it would be just about useless. Same thing goes for the environment in which the sound is heard.
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Good idea... grand idea. But it won't happen.
Best we can do is provide analogies... something is like this or that. But no static "measurement" of reality is possible.
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I like the idea and it should be done but I DO NOT expect manufacturers of air rifles to use the scale and standard in any meaningful or honest way.
Just like they measure FPS and FPE....
heavy pellet for high FPE
light pellet for high FPS
They will always be manipulating data. Some exceptions I'm sure.
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Working back from why we want to know this information, isn't the reason so we can compare our air guns and determine which is most silent or loudest? For my purposes I am good with a phone app and using it to compare my guns, trying to maintain the same environmental conditions while testing each gun. All I want the app to do is give me a decibel number so I can scale one gun against the others. I can "tare" the ambient noise out by observing the average noise level between shots and just subtracting from each gun's reading. Good enough for the girls I go with. Won't that get us all in the ballpark? Provided that we are all using the same app? But really...don't I already know my gun's sound hierarchy before I start? Taipan: sly smile 8). Blitz: The Feds are on the way :-[
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Working back from why we want to know this information, isn't the reason so we can compare our air guns and determine which is most silent or loudest? For my purposes I am good with a phone app and using it to compare my guns, trying to maintain the same environmental conditions while testing each gun. All I want the app to do is give me a decibel number so I can scale one gun against the others. I can "tare" the ambient noise out by observing the average noise level between shots and just subtracting from each gun's reading. Good enough for the girls I go with. Won't that get us all in the ballpark? Provided that we are all using the same app?
Yes to above. I've tried a couple apps and the measurements vary between them, so what. If I use the same app in similar conditions I can compare the Artemis to the Talon and the BSA. My ear knows who has the big mouth ;) ;) ;)
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When I am shooting the Marauder (.177) tuned by you know who, no one can hear it but me.
Why?
My ear is on the stock, the stock is attached to the action and, inside the action, things are moving (against each other).
How quiet is it?
Once when shooting at Ione, I missed two shots.
I took two more and my squad mates had no clue that I had..
We were shooting in 110 degree heat, that day..
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For my purpose if the gun action by my ear makes less noise by my ear than a starling exploding 40 yards away the gun is as quiet as I need it.
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What is a good decibel meter app for an iphone?
How many decibels is a P17 at 2, 10, 25 and 50 yds?
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I was shooting my R7 .177 yesterday afternoon just to get a break from the heavy hitters. The noise level was surprisingly so low I realized I was MISSING OUT by not USING the R7! Open sights.
Going to HW95L .22 this morning the noise level on these is always "subdued" compared to HW80s, which are eye opening in noise level to me (they wake you up when you fire them like the D54).
An R7 doesn't need a muffler at all at any range around here in this neighborhood.
The bass on cars driving by is what you hear when they are approaching from blocks away. This is an incident we all know is true--the song is muted out by the bass thumping a storm.
HW35Es have a shorter "burst" of sound more like a "boink" noise while the others going up in power have a longer lasting sound.
The decibel meter is confusing to me because you can have a rifle shooting ONE decibel higher and it can't be distinguished--or it is distinguished--without regard to what the meter says.
They say a .22 LR is loud enough to cause ear damage, but if you read the decibels on some of our rifles they shoot as loud as a .22LR according to the decibel meter.
Type of sound makes a difference and I hear "mechanical noise" in the HW80K .22 Long Range Hunter as pointed out earlier--also I hear mechanical noise in the HW98 which is not present in any R9 or HW95L. In the case of the HW98 the stock and metal rods transfers the machine vibration noise directly into your ear that is near the stock.
The D54 .20 has no mechanical noise, or if it does it is so low I can't hear it. All I hear is the sound of the pellet leaving the muzzle and then slamming into the trap instantly. No mechanical noise at all. I think the sled system relieves the stock from transferring the noise from metal to wood to ear. It all ends up being a loud puff of air is all.
The HW44 pistol in .22 is stunningly silent--more silent than the D54 or even an R7. It just "clicks" and a .22 pellet is sent downrange at 730 fps!
The loudest rifle I have is the HW80 .20 followed by the HW80 .25 and HW80 .177. I think that's because the HW80 .20 is shooting more on the "hot" side and always did the time I got it.
Anyway, the other thing is what sounds loud to me may not be the same for others since I do have impaired hearing on some frequencies. I was in FA (LIGHT) and AR (HEAVY) in my first Army units.
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Relatively speaking, it takes 3 decibels to be heard as a difference in sound.
Factor in, however, a woman's hearing being 6 decibels more acute than a man's. And remember, decibel incrementation is not linear, it's logarithmic.
So if you have a female in your life... beware. She has opinions on your guns' sounds that are different from yours.
Have fun with those meters. :)
https://www.leonardsax.com/wp-content/uploads/2015/01/2010-Sax-hearing.pdf (https://www.leonardsax.com/wp-content/uploads/2015/01/2010-Sax-hearing.pdf)
https://en.wikipedia.org/wiki/Decibel (https://en.wikipedia.org/wiki/Decibel)
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Relatively speaking, it takes 3 decibels to be heard as a difference in sound.
Factor in, however, a woman's hearing being 6 decibels more acute than a man's.
My wife can hear me and a buddy mumbling from 100'... "What did you just say"
Caught talking about women or whatever.
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some things to ponder...
what kind of door slam? solid pine? solid oak? hollow core? steel? how much force is used to slam the door?
what size hand is clapping? are the palms cupped or flat? is it a clap you would use at a ball game or a recital?
whispers can be very subjective.
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What is a good decibel meter app for an iphone?
How many decibels is a P17 at 2, 10, 25 and 50 yds?
Direction is important. 2, 10, 25 yards in front of the muzzle, behind the shooter, in open air, all directions?
Sound pressure levels drop off exponentially. Sound sources can be directional (guns, speakers) or not (jackhammer). Surfaces in relative close proximity will cause sound energy to bounce off and increase sound levels for pulse events.
Continuous sound can be cancelled by imparting by adding sound energy at same frequency but 180 degrees out of phase (Bose noise cancelling, Helmhotz resonator). Singular events, very hard to do this actively or passively, as you need the exact frequency.
Now frequency: some people are more or less sensitive to specific frequencies, so the same noise will seem louder or softer.
Singular pulse events like an airgun report or pellet impact have multiple frequencies involved.
When you look at a sound event on a spectrum analyzer, you will se multiple frequencies. To attenuate, you need to target those frequencies, assuming they are the same every time. Will shooting heavy pellets produce the same frequencies as light pellets?
Don’t want to dissuade, but this is very complex stuff.
At work, when we specify permissible sound levels for machine operation, we state the background sound level, then distance from the front of the machine, height of the recording device (to simulate the operator), the settings of the meter (fast, slow response, A B or C), and the room conditions ( drywall, 8’ Tile ceiling , concrete floor, 10x10’ room). This is the likely use scenario.
Hope this is helpful.
JMJ
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All good stuff, John. But after deleting a similarly long post I just shortened it to what I said in Post #10.
It's not going to happen. We can go on about pulse amplitude and duration, frequency, reflective concentration and cancellation, and directional specificity et cetera and it will be a kite without a string... gone in the wind.
I spent most of my professional life involved in sound in one way or another. Trying to explain it all to someone who just wants a standard microwave dinner is impossible. So I just cut to the bottom line.
Again, the best way to convey comparative differences to a diverse audience is to provide an analogy that everyone can relate to, it's done often.
Like these and even those are ambiguous.
https://www.chem.purdue.edu/chemsafety/Training/PPETrain/dblevels.htm (https://www.chem.purdue.edu/chemsafety/Training/PPETrain/dblevels.htm)
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And while the effects of our guns' differing sound outputs has been noted, it hasn't been quantified.
Part is because of all the rest mentioned proceeding this, but some is because of the old Fletcher-Munson curves... something most? are familiar with although likely tangentially.
https://en.wikipedia.org/wiki/Equal-loudness_contour
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Hey John I tried looking this up but couldn't find any info on it, maybe you know it offhand. What's the maximum allowable loudness for brief exposures to sound? I.E. how loud can repeated short exposures be in order to be considered hearing safe?
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Sorry, Not exactly sure.
My experience is with machine noise from medical equipment; If you can hear the alarms while a machine is operating, operator comfort level, etc, plus what I remember from engineering school 30 years ago.
JMJinNC
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My wife says I have the loudest applaus she has ever heard. I also am the last one to clap... Twice.
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Hey John I tried looking this up but couldn't find any info on it, maybe you know it offhand. What's the maximum allowable loudness for brief exposures to sound? I.E. how loud can repeated short exposures be in order to be considered hearing safe?
Not to speak for John, but the answer isn't simple, nor the diagnosis if it does happen.
That said, one knows when a sound is too loud. The advice is, obviously, to avoid repeating it if it's accidental, and to take protective measures if you intend to be where or do what is making that noise.
Here is more on the subject: https://www.cdc.gov/nceh/hearing_loss/how_does_loud_noise_cause_hearing_loss.html (https://www.cdc.gov/nceh/hearing_loss/how_does_loud_noise_cause_hearing_loss.html)
As can be surmised, the effects can be unnoticeable... for a while, but they're cumulative. Many are living with hearing losses without knowing it. If you live long enough you will. Provide for then.
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Yeah I'm super careful with my hearing, no worries about that. I was just wondering if there were any exposure limits set for brief noises like there are for continuous noise. Obviously any noise that would be considered safe for eight hours straight would also be safe for brief exposure.
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Travis,
Goal statement: To find a more meaningful sound measurement method, for evaluating airgun discharge noise.
The most objective methods use expensive calibrated dB meters, placed in precise geometry with the muzzle. Rather than trying to improve the industry standard on the cheap, I say throw it all out.
Some have suggested comparing the shot to a reference sound. That is a good plan. It leads to my method:
Play the video below (or equivalent) at high (known) volume, adjacent to your shooting position. Shoot while the music is playing, and with it off. Take turns walking off to stop and listen at 5 or 10 yard increments, or to a meaningful distance (such as your fence line). Obviously, there should be zero risk of shooting the person "wearing the ears". That said, I prefer doing this on my own, by using a smart phone as a recording device - explained below.
The question is not how many dB can you measure at 10, 25 or 50 yards; but at what distance does the sound of the shot grab your attention. By itself, or over percussion music (or any reference sound you care to use).
Now, you can come up with any variation on this theme. The point is that the tone, abruptness and duration of the sound usually matters more, than the measured peak value. This is highly subjective, and does not rely on phone apps, for those too cheap to buy a proper short duration dB meter.
One of the main reasons for the music (played on a loop), is "one person operation". It enables you to use a smartphone at the "ear distances" you care about. Without the music or background sound of steady predictable level, the phone's microphone gain will drift up to its maximum value. Thus the sound of the shot will seem louder than it really is. Feed the microphone constant sounds and its gain settles at a more reasonable value. Exactly what that gain is, matters not; because your airgun muzzle and the music speaker are the same distance from the microphone (required for this "test"). Thus, when you play back the recorded music with the shot/s overlaid on it, you judge if the sound is louder, sharper, more obnoxious than the music.
Of course, a proper recording device with adjustable but fixed microphone gain would be preferred.
For those of you who scoff at the idea that a smart phone, because it can't possibly record a realistic likeness of an airgun discharge, I have this retort: If the phone's electronics are not up to recording the sound accurately, with you as the calibration device, do you think that it will do any better with some app you downloaded?
By the way; place your (soft) backstop as far away as you can, so that the report and terminal impact can be distinguished separately. When your report is muted, the impact of the pellet is usually the most obvious sound. It makes me laugh when someone demonstrates a suppressor, while shooting at a steel plate 10 yards away. They seem to do this to prove they "can hit a target", or "not to waste the shot". Meanwhile, the steel ringing, drowns out what I am trying to hear.
Also, don't play the music or reference sound so loudly that it annoys the ears you are trying to avoid, in the first place. Work up to a reasonable volume. The distance where it is just detectable to the "naked ear" is one of your benchmarks. When it grabs attention would be another. Now, does the shot sound louder, quieter, or similar to the music? At what distance do they blend in with the typical background noise for that time of day?
Place your ears or mic in the direction and close to the ears that matter.
So, this is not so much a standard test, as one that is easily customized for your local conditions :)
Unusual percussion music: https://www.youtube.com/watch?v=FqJdzYY_Fas&feature=youtu.be (https://www.youtube.com/watch?v=FqJdzYY_Fas&feature=youtu.be)
Right click video window to select "loop"...
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Two more things:
Use your smart phone's video to capture the audio. It has a wider range of sounds that it can capture, compared to the voice recorder.
Don't use your phone too close to the muzzle. The sound recording will clip over a certain level, even with the sound meter apps. That will flatter the result. Besides, who cares how loud your airgun is one meter from the muzzle? The ears that matter are bound to be further than 10, 20, 30, 40 or 50 yards...
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The standard why of measuring the report of and air rifle is using a meter and capturing the Db level, this system is very flawed and really tells the customer very little. Db meters you can buy really have a wide range and back groud noise and where the meter is located can have wide effects in readings, also most people have no idea what 1 dB is and how it effects what you can hear. I want to start a industry standard using a scale based on known noise levels and then scale that 1 to 10 what do you all think? Like for example 1 being a whisper 3 a hand clap 7 a door slam 10 a shot gun...something like that
Only problem with that is that, since the decibel scale is kind of a logarithmic scale, you should probably go up to about 10,000 for really loud sounds. You would also need to do your reference source at the same time (if you're thinking hand clap, how hard a hand clap?). Meters are good, but you have to have the correct response. You also have to have the correct set up. This is usually 3 ft. off the side of the muzzle, outside, with no buildings near to echo sound. (or you could build an anechoic room).
https://www.cirrusresearch.co.uk/blog/2015/01/fast-slow-impulse-time-weightings/ (https://www.cirrusresearch.co.uk/blog/2015/01/fast-slow-impulse-time-weightings/)
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You want a standard balloon pop sound? How about this:
https://www.amazon.com/Industrial-Pre-filled-Blubonic-Industries-Cushioning/dp/B0191HO1P2 (https://www.amazon.com/Industrial-Pre-filled-Blubonic-Industries-Cushioning/dp/B0191HO1P2)
Just step on it abruptly...
(https://images-na.ssl-images-amazon.com/images/I/71Sy%2BDuB4HL._SL1500_.jpg)
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When I read the specs on an air gun and the noise level is rated as "LOW", I have never been disappointed. The gun has been quiet enough for my back yard.
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I appreciate the intent expressed in the OP: To compare airgun discharge noises against common sounds; such as a whisper, or a car door closing. The snag is calibration. I hope the idea below helps address calibration, so that people could make their own "GTA standard" rig:
The images below are of a simple "Gravity Clapper" I dreamed up. Its exact dimensions are totally negotiable. My suggestions would be to use standard wood sizes and types.
As a place holder for dimensions, I came up with:
A base that is 12" square by 1" thick. If the base is not heavy enough, it can be made larger or thicker.
The "clapper" is 6" square by 2" thick.
The dowel is one inch in diameter, with a series of through holes 3/16" diameter, spaced 4" apart, starting from the base as "zero". The dowel is 48" long and would be pressed or glued into the base.
The "pin" is a piece of wire with a loop at one end, so one can jerk the pin out, by means of a length of cord.
I added rubber feet so that the base would "ring". It might ring better with the feet placed more inwards, but the rig would be easier to pull over with the "feet" closer together. One could use three feet to ensure the rig did not rock on uneven surfaces. As long as two feet were placed in such a manner as to best resist the pin extraction friction force.
I considered spacing the pin holes so the gravitational potential energy doubled with every increment. However, that results in fewer than 10 increments, unless the dowel is made rather tall. The way it is, each input energy increment is the same, so the change in sound would be more gradual, with more resolution all the way through the range.
Anyway, I am full of ideas. Many of them silly....
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Good points above, Subscriber!
I see a lot of variation in how people use those meters...I am a fan of recording the entire acoustic event for analysis and comparison later. It is really important to be repeatable in this kind of work. My wooded back yard versus an open field--different results. Get the mic turned a little different than last time--different results! Weather conditions and so on. Back to back tests are easier, but taking it down and setting up again is the tricky part. Bring a tape measure, marking stakes or whatever and take notes!
Anyway, like you were saying about what the shooter hears versus someone down range. The 1st person experience is relative and interesting to know, but that sound down range is the important one. And for that repeatability is the key, e.g. 20 feet down range and 20 feet off the line of fire, with the mic perpendicular to the trajectory (or pointed at the shooter, if you prefer). Not too close, but not too far away either. And don't forget to use a dead silent or at least quiet target...don't want to measure the impact too.
We just need something realistic, repeatable and easy to remember to set up the next time. Oh look--3 R's of testing!
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Yes, David
I think that industry standard suppressor testing protocol answers the question, "is it hearing safe"; at the shooter's ear? of course, measuring the sound right by the shooter's ear, better answers that.
The more pertinent question for airgun shooters appears to be, "is it likely to bother the neighbors". As such, measuring or evaluating the sound much further away from the muzzle seems obvious.
I can hear car doors slamming several houses away, because low frequencies carry much further than high frequencies. However, it is a cracking sound that makes my ears ^#(*% up, with "what's that?". Something like the sound of a large twig snapping, is more attention grabbing to me than a dull thud. On the other hand; any sound that is unusual for the time and place will draw attention. Especially a sound that is repeated multiple times.
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Maybe fired in a recording studio or hearing test booth..
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I believe the system will need to be two part as described above, one for the report and one for the mechanical noise then a cumalitive number for both. For example 5 report 2 mechanical 7 total. Now to get base measurements that make since for anyone in the world.
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Maybe fired in a recording studio or hearing test booth..
The studio isn't so important as just being aware of the surroundings. An open grassy field has about zero "echo" other than the real echo off the tree line or buildings far enough away to notice the return. When closer to buildings, trees and other things, the strong pulse from the shot (or any loud noise) bounces right back at you and gets all over the data. I jest some, but I can almost count the trees in my yard from the spikes the recording picks up.
Just for kicks, I've been reviewing the audio of the "open field" test at different playback speeds.
Attached is a screen shot of the test in Audacity. The session has been snipped to shorten the dead time between equipment changes and maybe even the reloads. The first shot is an unloaded 1377 being used as a reference. I didn't note how many pumps--just messing around that day to see what I'd get. That is followed with two shots from the R10 into a duct seal target box at 30 yards, with the stock shroud and an added suppressor (not a great one, by the way). Then two more shots with just the stock shroud and no added equipment. Finally two shots with the shroud removed. Everything happens at about 5 second intervals after the snipping.
At normal speed, with headphones on you can barely hear the bolt as as I cock each gun over the noise of the crickets (before the shot for the pistol; after the shot for the R10--I reload after my shots). You can also hear the echo of the open space I am in on the pistol and unshrouded R10 shots. Unless your ears are really good, you can't pick out the impact at the target 1/10th of second after the rifle shots. But you can see the impacts in the screen shot in Audacity (attached). I could have moved the box way out, but it was 30 yards as it was and I didn't want to shoot into the dirt in this "borrowed" field. The mic was set up half way between the shooting position and target and maybe 10 yards off the pellet path.
But listening at 1/3rd speed is awesome, crickets, echo and all. Especially of note is the tone of the shrouded results--they almost whistle. That makes me think shrouds and LDC might howl and whistle a lot, but we just don't notice. But game might...so watch those internal edges if you are making your own parts. My USB microphone was software limited to 20kHz, so it wasn't going to catch any really high frequency stuff.
Interestingly, I can see a hammer bounce in the pistol shot and two bounces in the unshrouded data. A close up of that is also attached and you see the hammer strike, the shot, and two bounces. That 1st bounce is letting some air out; the second is just mechanical noise or very weak, I think. The shroud alone muddles the details, but I can make out the hammer, shot and one bounce. Shroud and LDC muddles it further and I can't distinguish the parts.
So, let me backtrack on the studio. If you want the gory details, a studio will work and take care of the crickets too ::), but otherwise the key is avoid cluttered surroundings and think of the timing of any echoes.
If I can figure out a way to link the audio, I'll add post those. (Audio attachments are allowed at this level in the thread and the media section isn't accepting MP3 files...)
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I believe the system will need to be two part as described above, one for the report and one for the mechanical noise then a cumalitive number for both. For example 5 report 2 mechanical 7 total. Now to get base measurements that make since for anyone in the world.
Travis,
I don't think sound adds in a meaningful way, because it follows an inverse distance squared function. The sound generated nearer to your ear (or conducted by your cheek bones) will sound louder to the shooter. For example; mechanical vibration from a springer sounds louder to the shooter than to someone 10 yards away.
Might it not make more sense to offer two measurements, described as "shooter's ear", and "bystander" (at some specified distance greater than one meter)?
Let the mechanical and air noise values combine as they are perceived, or measured; rather then simply adding them mathematically. This means that a springer may score "loud" to the shooter, while medium to the bystander. Compared to a PCP, that may be quiet to the shooter and medium to the bystander; because the latter are more exposed to the muzzle.
In absolute terms, one would expect the shooter scale to be louder than the bystander scale; because sound level drops off with the inverse square of the distance. And because sound from the muzzle is directional. This does not matter, unless you try to add different sound measurement values.
When I want a better idea of how loud a springer would be to an observer, I fire it horizontally from waist level. This happens anyway when I want to measure muzzle velocities with my chrono placed on a 30" high table.
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I believe the system will need to be two part as described above, one for the report and one for the mechanical noise then a cumalitive number for both. For example 5 report 2 mechanical 7 total. Now to get base measurements that make since for anyone in the world.
Travis,
I don't think sound adds in a meaningful way, because it follows an inverse distance squared function. The sound generated nearer to your ear (or conducted by your cheek bones) will sound louder to the shooter. For example; mechanical vibration from a springer sounds louder to the shooter than to someone 10 yards away.
Might it not make more sense to offer two measurements, described as "shooter's ear", and "bystander" (at some specified distance greater than one meter)?
Let the mechanical and air noise values combine as they are perceived, or measured; rather then simply adding them mathematically. This means that a springer may score "loud" to the shooter, while medium to the bystander. Compared to a PCP, that may be quiet to the shooter and medium to the bystander; because the latter are more exposed to the muzzle.
In absolute terms, one would expect the shooter scale to be louder than the bystander scale; because sound level drops off with the inverse square of the distance. And because sound from the muzzle is directional. This does not matter, unless you try to add different sound measurement values.
When I want a better idea of how loud a springer would be to an observer, I fire it horizontally from waist level. This happens anyway when I want to measure muzzle velocities with my chrono placed on a 30" high table.
Very good points! Thinking of a different approach now. THX
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I know I'll never get clinically accurate sound measurements with my (lack of real) equipment.
But for my own personal anecdotally relative values I go into my closet, close the door and shoot the gun (un-leaded) at the ceiling with my phone's decibel app turned on, the phone is left in the same place and same orientation (face up) each time. Guns are shot with their muzzles at the same height from the floor and then I compare the readings from the app.
I know this is HUGELY unscientific, but that's all I got and I find it is fairly repeatable from gun to gun. Of course firing WITH a pellet might make all the difference in the world and maybe one gun that's louder unloaded will be quieter discharging a pellet but like I said ... no other equipment.
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Assuming you meant "un-loaded" instead of "un-leaded"... don't do that with a Springer. ;)
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Assuming you meant "un-loaded" instead of "un-leaded"... don't do that with a Springer. ;)
;D ;D ;D Yes, I meant unloaded, oh wait, maybe I DID mean unleaded, but of course I never test springers anyway, leaded or not - because springers are Evil (but seemingly only to me) :(
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In the case of very loud airguns (high power, without contained muzzle expansion volumes), we do care about sound pressure levels at our eardrums when we shoot.
For lower power airguns (with contained muzzle expansion volumes), hearing damage is not much of a consideration (unless you shoot it in a small room, or with the muzzle pointing at and near a hard wall, without hearing protection).
So, it is my considered opinion that the overriding consideration for an airgun sound evaluation system is:
At what distance can the sound of your airgun being fired;
(a) be detected at all; and
(b) at what distance does it suggest "gun shot"?
This, where the human ear (or repeatable analog) is the instrument used to make these evaluations.
Perhaps you might argue that I have "a" and "b" backwards, but at least we would be talking "meat and potatoes".
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Subscriber, your second sentence above reminded me of what happened when I shot my R10 at a 4"x4" piece of tough plastic about a foot from the muzzle... The plastic took the shot just great, but I was not prepared for the noise--between the blast essentially reflected right back at me and the "acoustic" reaction of the plastic getting hammered by a pellet it was the loudest event I've let my ears hear unprotected in a long time. They were ringing for a moment and I was kicking myself for not realizing this was a hazard. And this was a shrouded rifle!
As for the perceived sound at other distances, I was thinking of that today too. I managed to get a "video" of the sound recording of a shroud test I did for the R10. It was my first test in an "open field" to minimize the effects of anything in close proximity. While reviewing the test and messing with video settings, it crossed my mind I should try this with two computers and two microphones. The one "near" the shooter and target is what I did last year, but I should add one that is like 50 yards away for comparison.
Next time.
Meanwhile, here's that video. It's just a screen grab of Audacity playing the recording, first at normal speed and then slowed like I was describing. I was also playing with new-found toys to create a video like this--a first for me. Though all my settings were maxed out, it isn't very loud because I was trying to faithfully capture the loud blast of the naked barrel of my R10 and because it is just a "pop" in a field full of crickets. Get your headphones on and turn it up until you hear the crickets and maybe even a low rumble in the background for the best effect.
Anyway, there are a couple of takeaways from a sound measurement:
- Audicity can do the sound level measurements, though not in a "calibrated dB meter" sense. I didn't realize I could use it this way until I was almost done messing with things today, but there is a "VU meter" type display at the top of the Audicity screen that will "hold" peak levels, letting you get an idea of dB level changes from one configuration to the next.
- Measurments can get tricky. I had to place the mic and mess with recording levels so I wouldn't exceed my measurement range. The "naked" R10 almost went over the top.
- Adding a reference measurement to every test will help with comparisons later, especially if done days or even weeks apart. Of course, careful attention to repeatable test procedures is important too, but some sort of "standard" sound would be useful. In this case, I used an empty Crosman 1377 pumped up some number of times (I forget how many). It was convenient and repeatable. Almost anyone can find one somewhere. There are other ways, but it seems an air burst of some sort makes a nice standard reference. Other ideas?
- The sound at normal speed is what we and the neighbors are going to hear, but playing it back at slower speeds or zooming in on the details shows us things that are going on. For example, someone with good ears may hear the "blat" of the hammer bounce in this R10, but a closer look certainly shows it, though I had to take the shroud off to get a clean measurement (the shroud takes the distinctness out of the sound). A really close look showed the 1377 hammer actually bounced twice--not that it matters much, but I can barely see that the second bounce is in the data. Slower speed playback really drew out the tone difference to me. And that echo is just cool to hear. It's the sound of the blast echoing off trees and structures off in the distance and into the woods, rolling along the hills. Like a miniature version of setting off an Big Blast on a 2 liter bottle out in the hills--hilariously awesome roll from that!
- I haven't tried it with this data yet, but you can do your own dB calculations from a recording if you really want a number. Calibration is the tricky part (use that reference measurement!), but that doesn't affect comparisons you can make with your equipment in back to back tests.
- Think about where that pellet has to go as part of your test. If the trap or target is too close (or too noisy), it will overlap your report of the shot.
https://www.youtube.com/watch?v=g1ishPFD9m8 (https://www.youtube.com/watch?v=g1ishPFD9m8)
Awww...anybody see that typo? Oh well.
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Good stuff, David
I think having crickets in background provides a clue as to how the sounds compare.
The recorded shot sounds have a lot of "sharpness" to them. I think it is that sharpness that draws attention; especially if it is repeated at fairly short intervals.
Of course the sharpness could be buried in a more distracting sound, such as an inner tube exhaust whistle (video below). Easily done, if you have a bottle of HPA handy :)
The proper way to make a Mini Cooper sound like an open exhaust Corvette, is to stretch the inner tube with a small rectangle of plywood or Masonite inside. Then to have about 1.5" length of inner tube free to flap at the end. That is how I made them 42 years ago...
https://www.youtube.com/watch?v=VVPU_3OqM4w (https://www.youtube.com/watch?v=VVPU_3OqM4w)
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(https://upload.wikimedia.org/wikipedia/commons/f/f4/300x0w%283%29.jpg)
Well there's this reference scale.
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The standard is @1M with a calibrated device. It's actually very easy to get accurate and consistent readings above 60db or so.
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It's actually very easy to get accurate and consistent readings above 60db or so.
Quite bit of discussion, technical references, and some testing with high quality microphones on pages 7-9 of this thread. https://www.gatewaytoairguns.org/GTA/index.php?topic=118339.120 (https://www.gatewaytoairguns.org/GTA/index.php?topic=118339.120). An overview of the topic here http://www.smallarmsreview.com/display.article.cfm?idarticles=2907 (http://www.smallarmsreview.com/display.article.cfm?idarticles=2907) while it is for PB's, the discussion applies to AG's.
The basic challenge is the fast rise time of the airgun impulse sound. If the microphone is not fast enough, then it is not clear what is being measured. The other question is why the measurement is being made. If you are interested in kid's hearing damage while they are shooting, that sensitivity depends on how fast the impulse is . If you are interested in not being heard by the neighbor further away, the perceived loudness also depends (but differently) on how fast the impulse is.
Lots of interesting reading available. There are standards and sound meters out there. How well they apply to what you are interested in depends on the details.
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From what I can determine this subject has already been figured out.
Since air guns are the subject, and that subject has been subjected to sound level tests ad infinitum, the relavant data already exists. We don't need to compare it to military jet aircraft using afterburners on takeoff... just other airguns. Right?
Will the sound level of any airgun influence one's chance of buying it? If so, read the reviews.
That's what the internet is for. It is the accumulated human knowledge base. Those looking to expand on it better have very deep pockets, an uncanny reputation for good luck, membership in Mensa, or lots of buds and friends to share it with while they reinvent the wheel.
:)
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It's actually very easy to get accurate and consistent readings above 60db or so.
Quite bit of discussion, technical references, and some testing with high quality microphones on pages 7-9 of this thread. https://www.gatewaytoairguns.org/GTA/index.php?topic=118339.120 (https://www.gatewaytoairguns.org/GTA/index.php?topic=118339.120). An overview of the topic here http://www.smallarmsreview.com/display.article.cfm?idarticles=2907 (http://www.smallarmsreview.com/display.article.cfm?idarticles=2907) while it is for PB's, the discussion applies to AG's.
The basic challenge is the fast rise time of the airgun impulse sound. If the microphone is not fast enough, then it is not clear what is being measured. The other question is why the measurement is being made. If you are interested in kid's hearing damage while they are shooting, that sensitivity depends on how fast the impulse is . If you are interested in not being heard by the neighbor further away, the perceived loudness also depends (but differently) on how fast the impulse is.
Lots of interesting reading available. There are standards and sound meters out there. How well they apply to what you are interested in depends on the details.
Interesting. So it appears as if manufacturers are cutting corners and (shocker) that $20 sound meter may not be adequate. That said, provided you have decent equipment, it's easy to set up. You will note, though, that your ear is much closer than 1m from the end of your barrel, and almost none of the airgun review sites seem to be using a 1m distance.
As for sound in airguns, a few basics still apply:
Subsonic will always be much quieter than supersonic. That crack isn't going to be lessened in any way by a moderator. Shoot heavy and slow as a rule to keep fps below 1100 or so in bigger PCPs and springers.
Air will be quieter than CO2 or some expanding gas under pressure, if the pressures are the same. (insert bit on physics and dissimilar substances/fluids)
Not all moderators are the same.
Indoors still requires hearing protection in most cases due to SPL levels and enclosed spaces. Always toss those muffs on and keep your hearing working into old age.
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You will note, though, that your ear is much closer than 1m from the end of your barrel,
and almost none of the airgun review sites seem to be using a 1m distance.
Sound is directional; and the airgun is between you and the muzzle. So, with a pneumatic it is going to sound quieter to the shooter than someone 6 feet to the side, but in line with the muzzle, front to back. Now, if you had a muzzle brake with rearward facing ports and a lot of blast, that might affect a few perceptions...
A medium power springer usually sounds louder to the shooter than a person nearby, because the spring and piston transmit vibration to the shooter's skull by conduction (stock cheek-weld), and springer muzzle pressure is not high, compared to a more potent, unshrouded PCP.
I also notice that airgun reviewers that provide instrumented sound readings seem casual about where the measurement device is placed. So much for standardized readings. I can handle them using their own standard (if they explain it), but to causally place the mic in a different position relative to the muzzle for every airgun they "test", is a bit much. It is like showing groups, shot at non declared, non standard ranges...
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This is an old report but it shows MUCH higher decibel ratings than other ones. Assuming all this is true, we should be wearing hearing protection. Does anyone here do that?
https://www.pyramydair.com/blog/2009/03/airgun-sound-level-measurement/ (https://www.pyramydair.com/blog/2009/03/airgun-sound-level-measurement/)
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Yeah, most of the measurements out there may be worse than useless, they can be misleading.
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4896309/ (https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4896309/)
One of many reasons to put an LDC on, especially if you are shooting indoors during the winter. A stock 2240 inside a garage or basement can get loud.
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.. Assuming all this is true, we should be wearing hearing protection. Does anyone here do that?
Many here report wearing hearing protection.
My past years of Powder Burners and working on Jet aircraft along with massive Db of rock music took it's toll long ago. ::)
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Sound level testing is or can be quite complex. But for the purpose of what we want, how "loud" is my gun, it doesn't have to be.
If one were to desire comparisons across many users, first a baseline would have to be established. Then, a portable calibrated means of measuring the gun which one would want to compare it to would have to be used for all comparison sampling.
See the link: https://www.youtube.com/watch?v=1sgyRJYvXt4 (https://www.youtube.com/watch?v=1sgyRJYvXt4)
By using random sample collection devices, you really don't know what the results mean because they would not be based on a reliable measuring system standard.
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Felix,
Instruments have their place. Especially if they can distinguish which frequencies sound louder to humans. That is what really matters; and human hearing is known to have a highly non-linear perception with regard to apparent sound level through the audible spectrum.
Most cheap hand-held sound measurement devices don't distinguish frequency. The better ones have a mode that mimics human hearing. All that are suitable for airgun discharge sound measurement have a "fast" mode, measuring and holding the peak sound level value of a short duration event.
The instrument in that video appears to monitor sound over a working day, because total hearing damage is exposure related, not just a function of peak sound level. This makes me think it is not appropriate for short duration peak sound measurement. Despite the elaborate calibration device and procedure that you are advised to use, when renting the instrument.
What amuses me is the sound measurement instrument should be recalibrated before every use. Not that in itself, but that the device used to generate the sound used for recalibration can be totally trusted to hold its calibration. To be fair; one has a cord and more exposure to factors that could damage it than the other.
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if we want to compare one instance of a noise level to another, a baseline would have to be established as to what is "loud". controlled sample collection and controlled units of measurement are a requirement to establish this baseline. then the same would be required to compare collected samples against the "loud" value. this can only be done with calibrated instruments and controlled collection within acceptable parameters. so, the sample collection methodology ultimately determines whether the samples are viable to make a determination on what is "loud" and what is less than "loud". loud is subjective, so a dBa of X would first need to be declared as what is "loud", then sampled levels would need to be collected and compared to what is "loud" to make a determination on whether the sample is above or below the declared level.
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Yes, Felix; "loud" is subjective. If your next door neighbor complains, it is too loud, no matter what your calibrated instrument reads. At the muzzle, or 50 yards away.
Let me try to keep this short: Unlike with firearms, measurements that are captured 1 meter off the ground and 1 meter to the side of the muzzle are not very useful with airguns. Not unless the point is to develop a device, to protect the hearing of the shooter (more likely with big bore airguns, or those exceeding 100 FPE).
Most airguns shooters care about how loud their airguns are, based on the perceptions of their neighbors; or their own family members even closer by. Neither of the latter care about actual dB. They only care about being disturbed by the noise; or not. Thus, to be useful to the majority of airgun shooters (who should speak up, if I am misappropriating them) want a system of sound measurement that more closely reflects backyard shooting concerns, than hearing protection.
I am not suggesting that instrumented measurements have no place. I am suggesting that the industry standards do not apply, and that new ones need to be developed. Such standards need to reflect the subjective needs of not even the airgun shooters themselves, but their disinterested neighbors. No easy task. One that hinges on subjectivity, not instrument calibration.
I would start the process by measuring the airgun sound at the distance neighbors ears are likely to be. As there is no standard for that, it will have to include multiple distances. With and without fences and hedges in between.
Not only does radiated sound level drop off by the inverse square rule, higher frequencies are naturally more attenuated than lower ones. So, any meaningful measurement system and standard must take these factors into account. Sound quality matters as much as sound pressure.
Who gets to decide what measurement methods and standards are appropriate? The first person or team to develop a sensible system...
Else, I vote for a free-for-all, allowing people to explain their system. If it makes sense it likely will be adopted. If it does not make sense, it will be rejected... Nobody is forcing anyone to abide by a given measurement system; except for the adherents to the "hearing safe" methodology used for firearm sound evaluation
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Just test a bunch of guns in the exact same way with a decibel meter. It's not rocket science.
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This is an awesome thread. 👍🏼
Subscriber's and other poster's comments clearly call for a purpose-driven method:
Measure what matters!
(In this case, not "need for hearing protection," but "bothersome noise perception by neighbors".)
Matthias
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The best system I have found to judge airgun noise?
A typical California neighbor!
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Man the love of California here is real... pretty funny.
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Yeah, if you made an LDC that chirped like the California gnatcatcher you would be set.
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Yes, Felix; "loud" is subjective. If your next door neighbor complains, it is too loud, no matter what your calibrated instrument reads. At the muzzle, or 50 yards away.
Let me try to keep this short: Unlike with firearms, measurements that are captured 1 meter off the ground and 1 meter to the side of the muzzle are not very useful with airguns. Not unless the point is to develop a device, to protect the hearing of the shooter (more likely with big bore airguns, or those exceeding 100 FPE).
Most airguns shooters care about how loud their airguns are, based on the perceptions of their neighbors; or their own family members even closer by. Neither of the latter care about actual dB. They only care about being disturbed by the noise; or not. Thus, to be useful to the majority of airgun shooters (who should speak up, if I am misappropriating them) want a system of sound measurement that more closely reflects backyard shooting concerns, than hearing protection.
I am not suggesting that instrumented measurements have no place. I am suggesting that the industry standards do not apply, and that new ones need to be developed. Such standards need to reflect the subjective needs of not even the airgun shooters themselves, but their disinterested neighbors. No easy task. One that hinges on subjectivity, not instrument calibration.
I would start the process by measuring the airgun sound at the distance neighbors ears are likely to be. As there is no standard for that, it will have to include multiple distances. With and without fences and hedges in between.
Not only does radiated sound level drop off by the inverse square rule, higher frequencies are naturally more attenuated than lower ones. So, any meaningful measurement system and standard must take these factors into account. Sound quality matters as much as sound pressure.
Who gets to decide what measurement methods and standards are appropriate? The first person or team to develop a sensible system...
Else, I vote for a free-for-all, allowing people to explain their system. If it makes sense it likely will be adopted. If it does not make sense, it will be rejected... Nobody is forcing anyone to abide by a given measurement system; except for the adherents to the "hearing safe" methodology used for firearm sound evaluation
I believe my point was lost when I provided a link to a measuring device that is used for TWA noise level recording. I provided that link simply to show that there is more to it than just point a mic at a source and you're good. I am addressing not personal protection from noise levels, but a standard by which one would measure sound levels where a measurement means something because the level is standardized by establishing a baseline, and using a calibrated device that measures dB based on a standard.
One can use a sound level meter for measurement and the results would not be accurate or meaningful to others if the method and device they use are not the same as what others are using. Even by using the Radio Shack sound level meter, results will vary from device to device because they are not intended to perform precise readings, but general sound level measurement.
So, we have to consider a baseline value, a standard based calibrated instrument, target frequencies to measure, and the environment that can give a wide range of reflective values.
Having said all that, using a cheap sound level meter 1 foot away from the muzzle and comparing that to what other people are getting from their phone app or random device can mean something for most people, but I think the OP was going for a standard. That's what I am addressing.
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Thanks for the clarification, Felix.
At the risk of repeating myself; two (different caliber/power/configuration) airguns that measure equally loud a foot from the muzzle with a calibrated instrument, most likely will not measure the same dB 25 and 50 yards away. So, close measurements may be useful to rank airguns as a starting point, but the value of such a system will come in when the ranking includes the distance we care about most.
An instrument that can capture and report sound quality objectively would be invaluable: The sound of someone stepping on a twig in my backyard is much more attention grabbing, than a much louder car cruising swiftly by. Ditto for anything that sounds like a gunshot, regardless of the actual dB.
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An instrument that can capture and report sound quality objectively would be invaluable: The sound of someone stepping on a twig in my backyard is much more attention grabbing, than a much louder car cruising swiftly by. Ditto for anything that sounds like a gunshot, regardless of the actual dB.
You're talking about taking into account frequency along with loudness, in particular those that stand out to human ears...which is exactly what the 'A' mode weighting of a db meter does.
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You're talking about taking into account frequency along with loudness, in particular those that stand out to human ears...which is exactly what the 'A' mode weighting of a db meter does.
Yes. "A" mode is a must. But it is not just frequency related. A sound that builds slowly is not as startling as one that is abrupt; even if the former is louder. How does one program an instrument to quantify a startling sound, VS something that is generally ignored? Perhaps a bit of clever programming can be used to filter for that.
Humans pay instant attention to certain sounds, instinctively. Even before we have figured out, who, what or why is making some sounds, we find them impossible to ignore, and very motivating. A screaming child is an alarming sound that cannot be ignored. A heavy twig snapping behind you, generates another alarm sound. It signals an animal or human that may be getting ready to harm you. If all your neighbors hear are "champagne bottles uncorking", they will think you have lot to celebrate. Rather than run, they may want to join you :)
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Meaningful, non-standard objective testing of LDCs, providing a better signal to noise ratio ( :) ) :
https://www.gatewaytoairguns.org/GTA/index.php?topic=182738.msg156082548#msg156082548 (https://www.gatewaytoairguns.org/GTA/index.php?topic=182738.msg156082548#msg156082548)