A Standard Testing Method

[MikeVV]

As copied from another post to make sure that you see it...

To Mr. Spook -

Have I upset you ? Gotta be cool and give me a thumbs down symbol...isn't that just cute ?
Well, by your own admission, you seem to get your information from papers, books. Reading, whatever. That's all fine, for you.

Me, I lived it, for one month shy of 20 years. No, I don't recall how many satellites that it was that I helped get into space. But I know that I worked in three different acoustic chambers, in two locations within the SoCal area, and one on the East Coast, over and over again, helping with measuring the..."actual sound"...emanating from special speakers within the chambers, and the vibrations (sound !) coming from the as tested, satellite.
One was a smaller room, but tall, one was about 60ft., by 60ft., and tall. The one out of state, is large enough to hold a full movie theater and seats !

These chambers are equipped with many...and various mic's to pick up the sounds. They are set at various levels around the spacecraft. There are a various amount of "large" speakers in various locations within the various chambers. These microphones are NOT the cheap $50 ones that are generally used in testing the sound emanating from air-guns ! The bosses, get really upset when one of the setup guys destroys one !

Hours, behind (not me) a computer, to download all of the data, and then complete the analyzing of said data.

So yeah...take it for what it's worth, I have a "little ACTUAL"... (20 years worth !) knowledge of sound, and how to measure it !!

Mike

P.s. - Funny too. There IS...a guy that currently owns a shop selling air-guns, works on, builds air-guns...that has the SAME thoughts that I do about cheap DB meters, cell phone accuracy ! Call around, you'll find him.

That's all I have to say...about that !

 

[BackStop]

As copied from another post to make sure that you see it...

To Mr. Spook -

Have I upset you ? Gotta be cool and give me a thumbs down symbol...isn't that just cute ?
Well, by your own admission, you seem to get your information from papers, books. Reading, whatever. That's all fine, for you.

Me, I lived it, for one month shy of 20 years. No, I don't recall how many satellites that it was that I helped get into space. But I know that I worked in three different acoustic chambers, in two locations within the SoCal area, and one on the East Coast, over and over again, helping with measuring the..."actual sound"...emanating from special speakers within the chambers, and the vibrations (sound !) coming from the as tested, satellite.
One was a smaller room, but tall, one was about 60ft., by 60ft., and tall. The one out of state, is large enough to hold a full movie theater and seats !

These chambers are equipped with many...and various mic's to pick up the sounds. They are set at various levels around the spacecraft. There are a various amount of "large" speakers in various locations within the various chambers. These microphones are NOT the cheap $50 ones that are generally used in testing the sound emanating from air-guns ! The bosses, get really upset when one of the setup guys destroys one !

Hours, behind (not me) a computer, to download all of the data, and then complete the analyzing of said data.

So yeah...take it for what it's worth, I have a "little ACTUAL"... (20 years worth !) knowledge of sound, and how to measure it !!

Mike

P.s. - Funny too. There IS...a guy that currently owns a shop selling air-guns, works on, builds air-guns...that has the SAME thoughts that I do about cheap DB meters, cell phone accuracy ! Call around, you'll find him.

That's all I have to say...about that !

MikeVV, I'll give you one thing...

You really know how to dig a hole. Unfortunately, you don't know when to stop digging.

You can be an asset here on AGN or just 3/5's of that. (smile)

And no, I am no angel... or rocket scientist. (chuckle)

 

[OldSpook]

Regarding the standard setup for the rest of us... We plodding pedestrians, incapable of actually measuring a thing either because we do not have the proper equipment or we simply lack the knowledge required.

There will be errors in our measurements. The real question is "how big". You see I could provide you with a 10 million dollar NASA sound lab and there would STILL be an error associated with the measurements. There is ALWAYS an error associated with any real world measurement. ALWAYS. It is the size (significance) of the error which matters. In all but the most exacting situations there is plenty of room for that error to exist without confounding the results to the point that they can not be interpreted. That is what we are after, a good (correct) interpretation of the measurements we take. Your phone and a little knowledge will take you a long way to being able to do that. Let me give you an example.

I have a couple of moderators that I run on my Condor. When I try to measure the actual noise level of my .22 Condor shooting somewhere around 70 fpe I can't get a good reading with my cell phone. It catches 81 dB just about every time if I place it at 15 feet and 3 o'clock. The mic on the phone just can't pick up a pulse that is that short and turn it into meaningful data. Proves Mike is right doesn't it? Sort of, yeah.

When I put a moderator on the rifle the pulse is removed. I can tell that with my ears. That pulse which is probably more than 6 dB higher than the phone picks up is GONE. Therefore there is NO NEED to measure it. The larger moderator which I built is about 190 CCs. The smaller moderator is about 140 CCs. The smaller uses Tesla Valves (I believe one vendor calls them Tesla Diodes). The larger uses "K"-Baffles. I tested those two moderators today. I used my cell phone to measure the sounds because the moderators "spread out" the pulse and the phone has no problem picking up THAT signal.

The larger moderator averaged 75.8 dBs over five shots and it did remove the very loud short pulse (the "crack") the microphone could not pick up. It shows a 5.2 dB improvement over the measurement for the bare rifle, but we know that we have no baseline because we can't pick up that pulse. The improvement is probably more like 12 dB over the naked bore. We can't know the exact number so .... Mike is right, sorta... yeah.

So 75.8 becomes our baseline. Now just stick with me a few more moments.

I then tested the smaller moderator. It is 26% smaller in volume than the larger one. Over five shots it averaged 72.0 dBs. Well that right there is 3.8 dBs better than the larger moderator AND in a smaller space. Could there be SOME error, absolutely. Is it enough to screw up the conclusion? Almost certainly not. Can I prove it? Yes.

The standard deviation of the large moderator was 1.64 dB. The standard deviation of the small moderator was 1.24 dB. If we add the SD to the average for the smaller moderator we get 73.24 and if we subtract the SD from the average for the larger moderator we get 74.16. Now I don't expect everyone to be a statistics guru but the reason that one standard deviation is significant is that it establishes a probability of error. We have just removed one standard deviation from the larger moderator and added one standard deviation to the smaller moderator. That is 2 standard deviations total. Here is an old post where we were discussing standard deviation. It is very informative. I am the "Guest" account there posting the graphics. It was a different incarnation of OldSpook. From the information at that link we discover the probability of any shot from the smaller moderator being louder than any shot from the larger moderator is LESS THAN 9% of 9%. That works out to less than 1%.. Even with the error included there is a less than one percent chance that any shot from the smaller moderator will be actually louder than any shot from the larger moderator. I dunno. Seems to me to be accurate enough if you know how to interpret your data but what do I know. I'm just a 70 year old man with nothing but "book learnin'"... no experience in the real world at all.

So that is my point folks. I used my crappy cell phone to tell me how much better one moderator was than another. STO is right about that "Tesla Diode" it's smart technology and only a hundred something years old. But they are no more right than Mike in the assertion that you can't study this stuff without high end sensors. How in the world did Tesla do the things he did WITHOUT AN ANECHOIC chamber and ten million dollars worth of NASA sensors? Musta been one hell of a genius... well he was... but

He also refused to take "it can't be done" for an answer!

 

[BackStop]

Regarding the standard setup for the rest of us... We plodding pedestrians, incapable of actually measuring a thing either because we do not have the proper equipment or we simply lack the knowledge required.

There will be errors in our measurements. The real question is "how big". You see I could provide you with a 10 million dollar NASA sound lab and there would STILL be an error associated with the measurements. There is ALWAYS an error associated with any real world measurement. ALWAYS. It is the size (significance) of the error which matters. In all but the most exacting situations there is plenty of room for that error to exist without confounding the results to the point that they can not be interpreted. That is what we are after, a good (correct) interpretation of the measurements we take. Your phone and a little knowledge will take you a long way to being able to do that. Let me give you an example.

I have a couple of moderators that I run on my Condor. When I try to measure the actual noise level of my .22 Condor shooting somewhere around 70 fpe I can't get a good reading with my cell phone. It catches 81 dB just about every time if I place it at 15 feet and 3 o'clock. The mic on the phone just can't pick up a pulse that is that short and turn it into meaningful data. Proves Mike is right doesn't it? Sort of, yeah.

When I put a moderator on the rifle the pulse is removed. I can tell that with my ears. That pulse which is probably more than 6 dB higher than the phone picks up is GONE. Therefore there is NO NEED to measure it. The larger moderator which I built is about 190 CCs. The smaller moderator is about 140 CCs. The smaller uses Tesla Valves (I believe one vendor calls them Tesla Diodes). The larger uses "K"-Baffles. I tested those two moderators today. I used my cell phone to measure the sounds because the moderators "spread out" the pulse and the phone has no problem picking up THAT signal.

The larger moderator averaged 75.8 dBs over five shots and it did remove the very loud short pulse (the "crack") the microphone could not pick up. It shows a 5.2 dB improvement over the measurement for the bare rifle, but we know that we have no baseline because we can't pick up that pulse. The improvement is probably more like 12 dB over the naked bore. We can't know the exact number so .... Mike is right, sorta... yeah.

So 75.8 becomes our baseline. Now just stick with me a few more moments.

I then tested the smaller moderator. It is 26% smaller in volume than the larger one. Over five shots it averaged 72.0 dBs. Well that right there is 3.8 dBs better than the larger moderator AND in a smaller space. Could there be SOME error, absolutely. Is it enough to screw up the conclusion? Almost certainly not. Can I prove it? Yes.

The standard deviation of the large moderator was 1.64 dB. The standard deviation of the small moderator was 1.24 dB. If we add the SD to the average for the smaller moderator we get 73.24 and if we subtract the SD from the average for the larger moderator we get 74.16. Now I don't expect everyone to be a statistics guru but the reason that one standard deviation is significant is that it establishes a probability of error. We have just removed one standard deviation from the larger moderator and added one standard deviation to the smaller moderator. That is 2 standard deviations total. Here is an old post where we were discussing standard deviation. It is very informative. I am the "Guest" account there posting the graphics. It was a different incarnation of OldSpook. From the information at that link we discover the probability of any shot from the smaller moderator being louder than any shot from the larger moderator is LESS THAN 9% of 9%. That works out to less than 1%.. Even with the error included there is a less than one percent chance that any shot from the smaller moderator will be actually louder than any shot from the larger moderator. I dunno. Seems to me to be accurate enough if you know how to interpret your data but what do I know. I'm just a 70 year old man with nothing but "book learnin'"... no experience in the real world at all.

So that is my point folks. I used my crappy cell phone to tell me how much better one moderator was than another. STO is right about that "Tesla Diode" it's smart technology and only a hundred something years old. But they are no more right than Mike in the assertion that you can't study this stuff without high end sensors. How in the world did Tesla do the things he did WITHOUT AN ANECHOIC chamber and ten million dollars worth of NASA sensors? Musta been one hell of a genius... well he was... but

He also refused to take "it can't be done" for an answer!

I have always wondered how a Tesla valve might work in a moderator design. I don't have the means to make one (AFAIK) for a DIY moderator, but the idea has always intrigued me ever since I became aware of it. So, for me, it will continue to be PVC, hair curlers, ScotchBrite pads, washers, etc, etc, etc... (chuckle) And I have had pretty good success! (imho)

Now, with the Fortitude, I simply don't need a moderator like I did with the Freedoms. But, I may start working on one for the Fortitude... if I can make it a "slip-on" unit like I had for the Freedoms. (smile) I don't have the capability to make a threaded model.