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Decible level at trap range during shooting?

Discussion in 'Shooting Related Threads' started by diverdick, Jan 5, 2010.

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  1. diverdick

    diverdick TS Member

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    Would anyone on TS have an idea about the sound level generated during Trapshooting. Just asking for reason of a possible Town Ordinance restricting noise levels.
     
  2. Jamnss

    Jamnss TS Member

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    Have never much thought about but will take my db meter with me to the Dixie Grand and test at different dist. and post them that eve after the shoot. Jeff Ryals
     
  3. wolfram

    wolfram Well-Known Member

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    I was fooling around with a dB meter from work at the trap range and found the peak noise standing next to someone on the 16 was 105-110 dB. Back at the scorer's chair at 29 yards from the house the noise was about 90 dB with shooters on the 16.

    The race cars at the local dirt track get up to 125 dB in the stands as a comparison. The gunshots really aren't that loud but they do tend to put people on edge more than uncorked V8s for some reason.
     
  4. Joe Potosky

    Joe Potosky Well-Known Member

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    Important from where it's measured.

    In New York (state law) it's measured from just outside the clubs property boundry, not at the shooting station or field.
     
  5. zzt

    zzt Well-Known Member

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    I brought my audio analyzer to the range to measure frequency distribution and noise level. I found the frequencies to fairly evenly distributed, and averaging 88 dBA, and slightly higher for dBC.

    I was standing 10' behind the shooters. For every doubling of distance you drop 3dB, so you'd be 85dBA @ 20', 82dBA @ 40', 70dBA @ 80', etc.

    Your local noise ordinance will say how the level is to be measured, from where, and how many samples. It may be broad spectrum unfiltered or dBA or dBC. It may be at a specific frequency, or a specific range.
     
  6. Setterman

    Setterman Well-Known Member

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    Call Island Lake Gun Club near Detroit, 248-437-2784. Talk to Pat Lieske. He has been in a noise battle with neighbors for years.
     
  7. 870

    870 Well-Known Member

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    I don't claim to know much about the technical aspects of the sound level readings, but I will tell you I know of a club that tested over 90 decibels at over 400 yards from the traps.

    Informal testing by the police had never shown a problem, then an engineering firm was hired to test and the trouble started.

    There must be different ways to do these tests?
     
  8. zzt

    zzt Well-Known Member

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    870, if you were to tell me what results you were aiming for, I could devise an SPL test gave you what you wanted. I'm sure that is what happened at the club you mentioned. The neighbors hired the engineering firm, who understood what was expected, and they got the result they wanted. If the club hires a different firm, the results would be much different. That's when the fun starts, when you try to explain science to a lay jury.
     
  9. spitter

    spitter Well-Known Member TS Supporters

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    Contact SAAMI/NSSF in Newtown CT...
     
  10. Barry C. Roach

    Barry C. Roach Well-Known Member

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    There is no way that anybody got a 90db reading 400 yds. away from a trapshoot, even if the measurement came from out front, without cooking the results.

    Environmentalists and homeowners' associations have a reputation for cooking the results to fit their own agenda.
     
  11. Jamnss

    Jamnss TS Member

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    The db level for the F-22 Raptor at 50 ft in full after burner is 149 db. Was in the car audio market for years and we had a couple of show vechicles that would gererate 160 to 162 db. The sound pressure level or db was tested inside the truck.It would take your breath away when it would hit a lowbass note. Thank GOD I am now in the Home A/V market.

    The thing to remember to gain only 3db you must double your output.
    Sounds louder than 80 decibels are considered potentially dangerous. Both the amount of noise and the length of time of exposure determine the amount of damage. Hair cells of the inner ear and the hearing nerve can be damaged by an intense brief impulse, like an explosion , or by continuous and/or repeated exposure to noise. Jeff Ryals
     
  12. 870

    870 Well-Known Member

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    Barry, do you really know what you are talking about? ZZT seems to. There are different ways of measuring the levels, and unless the law specifies which method, it's going to come down to which "expert" comes across better.

    ZZT, it has something to do with "slow", "fast" and possibly "impulse" modes. Slow and fast must come up with very different readings due to averaging of other ambient sounds. Some "experts" out there say the "fast" mode is the way testing should be done for this type of situation. I don't know much about this or how easily these different methods could be challenged, but I do know these results occur.

    I'm not saying you couldn't challange these results, but Clubs out there should not simply brush-off these concerns because of state "range protection laws" or that somebody at the club said trapshooting won't exceed "XX" decibels at the property line. The state laws are great, if you meet the requirements. Problem is, many do not apply if there is a pre-existing noise ordinance in place locally.
     
  13. BigM-Perazzi

    BigM-Perazzi Well-Known Member

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    90 DB from 400 yards? I'd have to see evidence of that also!!

    Our experience in Michigan is measurement from the property lines. Also, it's an averaged reading not peak. Then take into account the noise of traffic driving past your recording device. The guy mowing his lawn across the street... The advice to contact Pat Liske at Island lake is sound (chuckle) advice..

    Jim

    Hell, Michigan
     
  14. 870

    870 Well-Known Member

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    Jim:

    I am going to guess your "averaged reading" is what the engineers in this case called "slow" mode. Clun never had a problem with that method, always was under 70 dba (local limit). The last test using the "fast" mode showed very high readings, even exceeding the state level of 90 dba. Local law does not specify a method to use, and there were experts stating that the slow mode (good for club) was incorrect for this type of test (what else would you expect?).

    I'm interested in ZZT's comments on these different "modes" (my term for lack of anything better.) Testing was by a reputible engineering firm so I am assuming anything "fishy" would be in the parameters they were given to test, as opposed to simply fudging some results.
     
  15. BigM-Perazzi

    BigM-Perazzi Well-Known Member

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    870, I can tell you from working in an industrial environment, exceeding 90 DB in an environmental test, is VERY loud....
     
  16. Barry C. Roach

    Barry C. Roach Well-Known Member

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    870. I haven't seen any evidence that you know what you're talking about either. My experience is more practical than scientific, admittedly, but I can tell you that a sustained 90db reading from any direction of a trapshoot in progress stretches my credulity.
     
  17. 870

    870 Well-Known Member

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    Barry:

    I never claimed that I know anything about the science behind gun club noise levels, other than there are different methods of testing; but I have read engineer's reports on them. That's all I'm saying - I've read engineer's reports stating that the dba levels exceeded 90dba. Most of you guys feel those numbers are crazy, and maybe you're right, but it is a fact that that was the result of the tests.

    Again, I don't think "sustained" noise levels are what they were reporting, I believe it was a peak reading (actually hundreds of peak readings. That's why I was wondering if ZZT knew what the potential differences were between the different testing methods.

    Maybe this report was flawed. The issue was taken care of efficiently without having to hire another expert, so I don't know what parts of the report would have been discredited.

    I'm going to guess that the science part of the testing is pretty well settled; any strange readings would seem to result from the way the test was set up?
     
  18. diverdick

    diverdick TS Member

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    Thanks to all for the info. I will call Pat Lieske and see what solutions they came up with.
     
  19. mixer

    mixer Well-Known Member

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    Here's how the "slow" & "fast" modes work. In the fast mode the meter reacts quickly to sound levels, showing PEAK sound levels. In the slow mode the meter is damped and shows average levels. the effect of brief sound peaks is minimized in the slow mode.

    The use of the A or C scales is called WEIGHTING. In the A scale the meter measures in the 500-10,000 hz range which is the area of greatest sensitivity to the human ear. The C scale measures uniformly from 32-10,000hz giving an indication of overall sound level. So you can get different readings depending on the mode & scale.

    If one wanted to show excessive noise levels then they would use the fast mode and the A scale. Conversely if you wanted to show lower noise levels then slow & C are the way to go.


    Eric
     
  20. zzt

    zzt Well-Known Member

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    870, humans do not hear linearly. The curves are actually logarithmic. Google Fletcher-Munson curves and look at the image results. What you are looking at are loudness curves. Generally, the curve crosses the 1kHz line at the reference dB level.

    As an example, look at the 30dB curve. It shows a 1kHz tone to be perceived as 30dB "loud". Now look at 100Hz. The 30dB @ 1kHz curve crosses the 100Hz line at 52dB, and the 50 Hz line at about 70dB.

    Remember that dB is a logarithmic scale, so most people cannot fathom the difference between 30dB and 70dB. Think about this. 30dB is the level of the quietest room you are likely to ever have been in. Think of a very quiet house, no wind, no kids, no appliances, everything is still. That is what 30dB sounds like. Now go to the busiest super highway you can find. 70dB is what you hear standing 100' away. It is loud. Will you perceive that as louder than standing 100' away from a trap range? Yes.

    Now take a look at the 0dB curve. 0dB is generally accepted to be the threashold of human hearing @ 1kHz. Softer sounds in the 2kHz to 8kHz range are perceived as equally loud. Lower frequencies must be much louder to be perceived as equally loud. Look at the 20Hz. If I play you a 1kHz tone at 0dB and then a 20Hz tone at 80dB, you will tell me they sound equally loud. 80dB difference!

    The dBA scale simulates how people hear at low to moderate levels (every day sounds). It is very useful up to about 75dB to 80dB. As you can see from the curves, our hearing of low frequency sounds improves as they get louder. So for rock concerts and the like, the dBC scale gives a more accurate representation. The "Flat" scal makes no attempt to correlate level to human hearing. It just measures actual sound pressure per frequency.

    Fast and slow readings refer to the time slice the readings were taken at. Think of the difference between a VU meter and a Peak meter on your audio gear. One measures the "average" level; the other the "peak" level. Both measure in a very small fraction of a second.

    Low frequencies propagate better than higher frequencies. Sound is actually pressure waves in the air. You can hear someone calling you from farther away down wind than up wind. The lower the frequency, the farther it "carries". Some humans can hear frequencies below 20Hz. As I've stated above, shotgun muzzle blast is broad spectrum.

    So if one were to be intentionally dishonest without uttering a single false statement, they'd do the following. Wait for a day with perfect atmospheric conditions, steady wind and almost no humidity (absorbs certain frequencies). Then set the meter up for flat measurements and take a series of really long duration readings on the Fast setting at 20Hz. Set the trace line to hold at the highest peaks ever recorded. If that doesn't get the "desired" result, switch to impulse. Of course they would have to take a whole bunch of impulse readings, because most of the time they'd catch nothing. Sooner or later they'd get an impulse trace that showed a level "loud" enough to satisfy the neighbors wishes. If they still didn't have enough, they could go to a near neighbor's house and set up in a location where the geometry of the house and the garage, or wing of the house created an acoustic lens. Setting the microphone at the focal point of that "parabola" will really jack up the readings. Then they could "honestly" report they had tested across all frequencies humans hear in front of the Jone's house and found levels of up to XdB! See how easy it is to mislead with "accurate" information.

    870, if it ever comes down to it, hire yourself an expert witness or a good engineering firm. Make sure they come to court with audio gear to demonstrate to the jury what the actual sounds and levels were from a highway, or your gun club at the boundary, and at the nearest house. They will believe their ears.
     
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