Sound meter results

Sound meter results

Joined: March 1st, 2002, 12:22 am

April 26th, 2012, 4:56 pm #1


Since the chrony decided it was going t0o be photo-phobic again, I decided to break out the sound meter and get a mags worth of noise samples.

Before doing it though, I returned the shroud to factory condition except forI drilled 4 5/64 holes around the shroud about 3/4 from the breech end.

It does _change_ the sound of the discharge, but cant say its any quieter with the holes. 

Ok, got 6. Apparently the meter and the chrony belong to the union......

the readings ranged from 97 to just over a 100 db.

I held the meter about 12" from the muzzle, even witht he muzzle on the shooters left.


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Joined: June 15th, 2004, 11:49 pm

April 26th, 2012, 5:17 pm #2

I looked up a Decibel (Loudness) Comparison Chart and saw this:

"Level at which sustained exposure may result in hearing loss 90 - 95dB "
Hey Dan, be careful and dont shoot much, Dan, yo Dan, ya hear me LOL

Buster
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Joined: March 1st, 2002, 12:22 am

April 26th, 2012, 5:37 pm #3


Couple things I just thought of:

1) no idea if the thing is calibrated correctly. sticker on the thing says it was calibrated in '92. Its been on the shelf most of the time since then.

2) very real possibilty I dont know how to use it correctly. might be more to it than holding the button down during the sonic event and watching the meter peak.

3) Ive only run the tests _indoors_ with walls, floors, table tops and other hard reflecteive surfaces close by that are probably influencing the meter's results. Outside may give a lower reading

interesting to note that the droid apps showed a peak from 85 - 91 db, a relative magnitude quieter. The droid readings were taken in the same room at the same locations the SPL meter was used.

 


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Joined: June 15th, 2004, 11:49 pm

April 26th, 2012, 6:39 pm #4

but still high .
same chart info

Telephone dial tone 80dB
City Traffic (inside car) 85dB
Train whistle at 500', Truck Traffic 90dB
Jackhammer at 50' 95dB

I hear traffic noise out my back door at 5am and its loud and thats about 2 miles south and west of me with major hwy. traffic noise in my PU is probably high 90 (97PU) I'm about 1-1/2 mile from a rail switch center and the whistle blow all times day & night, its loud.
I just wonder what my neighbors think of me when I'm shooting in my back yard. so far I havent been reported, but?

Buster
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Joined: March 1st, 2002, 12:22 am

April 26th, 2012, 7:08 pm #5


I suspect a slight reduction in the SPL, but not much.

and all that means I need to work harder on the shroud......


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Joined: April 28th, 2010, 12:23 am

April 26th, 2012, 7:46 pm #6

Couple things I just thought of:

1) no idea if the thing is calibrated correctly. sticker on the thing says it was calibrated in '92. Its been on the shelf most of the time since then.

2) very real possibilty I dont know how to use it correctly. might be more to it than holding the button down during the sonic event and watching the meter peak.

3) Ive only run the tests _indoors_ with walls, floors, table tops and other hard reflecteive surfaces close by that are probably influencing the meter's results. Outside may give a lower reading

interesting to note that the droid apps showed a peak from 85 - 91 db, a relative magnitude quieter. The droid readings were taken in the same room at the same locations the SPL meter was used.

 


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Southwest Montana's headquarters for Airgunning Supremacy
Proud Sponsor of team_subsonic
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Joined: June 15th, 2004, 11:49 pm

April 26th, 2012, 8:50 pm #7

Since the chrony decided it was going t0o be photo-phobic again, I decided to break out the sound meter and get a mags worth of noise samples.

Before doing it though, I returned the shroud to factory condition except forI drilled 4 5/64 holes around the shroud about 3/4 from the breech end.

It does _change_ the sound of the discharge, but cant say its any quieter with the holes. 

Ok, got 6. Apparently the meter and the chrony belong to the union......

the readings ranged from 97 to just over a 100 db.

I held the meter about 12" from the muzzle, even witht he muzzle on the shooters left.


dr_subsonic's pneumatic research lab

the Lunatic Fringe of American Airgunning
Southwest Montana's headquarters for Airgunning Supremacy
Proud Sponsor of team_subsonic
You said
Before doing it though, I returned the shroud to factory condition except forI drilled 4 5/64 holes around the shroud about 3/4 from the breech end.
on the stripper , is it a snug fit to the tube, if so, drilling the holes like you did, no air getting back there to go out them holes. did you feel any air from them. I havent had my shroud off in awhile so I cant remember if it were grooves in the stripper end that would allow air>

Just a dumb thought, maybe???

Buster
\\\ X ////
one step closer to the ultimate goal

located a pic of the stripper. looking at the schematic looked like there was a O ring around the back of the stripper that may block air. the one shown must go around the stripper in front of the holes just in front of the muzzle.
Last edited by threex4 on April 26th, 2012, 9:12 pm, edited 1 time in total.
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Joined: March 1st, 2002, 12:22 am

April 26th, 2012, 9:17 pm #8


<img border="0" alt="Photobucket" src="http://img.photobucket.com/albums/v301/ ... ipper2.jpg">

Pellet would go to the left from this perspective. The barrel ends just to the right of the last big hole on the right of the O ring. The oring does seal to the interior of the tube, creating a very alrge chamber behind the muzzle and a small one just behind the end of the shroud.                 

My contention is that the stripper does little to divert air flow from the muzzle blast into to shroud, or into the small chamber created by the stripper and o ring. Because of that, the air column  just follows the pellet on out the front and doesnt get diverted nor slowed. and hence the pop......

 

To answer Buster's question, yes, I do feel some air from the holes.                                                              


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Joined: June 15th, 2004, 11:49 pm

April 26th, 2012, 9:38 pm #9

I remembered seeing you pic, just had to let the slow overheated brain to think, where LOL

Buster
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Joined: March 1st, 2002, 12:22 am

April 27th, 2012, 4:28 pm #10

Since the chrony decided it was going t0o be photo-phobic again, I decided to break out the sound meter and get a mags worth of noise samples.

Before doing it though, I returned the shroud to factory condition except forI drilled 4 5/64 holes around the shroud about 3/4 from the breech end.

It does _change_ the sound of the discharge, but cant say its any quieter with the holes. 

Ok, got 6. Apparently the meter and the chrony belong to the union......

the readings ranged from 97 to just over a 100 db.

I held the meter about 12" from the muzzle, even witht he muzzle on the shooters left.


dr_subsonic's pneumatic research lab

the Lunatic Fringe of American Airgunning
Southwest Montana's headquarters for Airgunning Supremacy
Proud Sponsor of team_subsonic
and I'm thinking there is an art to setting up acoustic testing....

Took the gun outside the lab, held the gun in one hand and the meter in the other, about 3 feet apart, and the meter about a foot below the muzzle...... 85 ish db average

forgot about using the droid outside and went back to SSR develeopment.... then remembered _after_ I'd pushed the shroud forward... Shot 8 inside with the droid app checking the sound levels..... 81 for a high and the rest 75 - 80.

Differences between the two devices: the Scot meter has to have the "On" button held to sample, and the doid is always on. Holding the Scot means its not always oriented the same way for every shot and/or  an inconsistent distance from muzzle to meter I just put my phone on its stand and it never moves during the test (it shows db reading, and a low/high entry).

conclusions: 1) probably gonna have to setup a "noise station", much like you'd have a chrony setup, for consistency  2) Not fully sure I understand how the meter works(even after reading the manual thoroughly), and what affect its placement and orientation during the test has on the results 3) the droid apps have been rooughly consistent between the two sessions, and the meter not.

So I think I'm going to bag the Scot meter for a time, use the droid and app for consistency, so I can get to actions of extreme prejudice against the gophers (hehe got up this morning to 2 inches of fresh wet snow at home, close to 6 in town, so the pesting may have to wait), and look for some web info on how to use the meter and acoustic testing setups......

 


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the Lunatic Fringe of American Airgunning
Southwest Montana's headquarters for Airgunning Supremacy
Proud Sponsor of team_subsonic
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