Sound meters vs. O'scope

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Hush
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Sound meters vs. O'scope

Post by Hush » Thu May 19, 2005 8:27 am

The problem with most sound meters is in the rise time, how quickly it responds to the sound being tested, microphone, sensitivity and selectivity.
Might I suggest something which I do not see anyone referring to here and that is an ocilloscope.
They can be rented at some electronic shops, I have not used one in years to be honest but they have quick rise times and can also freeze the pattern that appears on the scope so that it may be photographed.

Another point I'd like to make is that some people are using Radio Shack sound meters which are not meant for this type of service ( short impulse of short duration)).
There is one airgun retailer that uses one for sound measurments for PCP air rifles ( these use pre compressed air to over 3000psi and can sound as loud as a .22rf.) He publishes db. ratings for each rifle he sells ( some air rifles come with built in moderators) These db. measurements are not true readings but can only give one a relative idea between different makes and models (comparative) but one cannot say rifle "A" is 1db. quieter than rifle"B".

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It is in the PLAN

Post by PCArms » Thu May 19, 2005 8:39 am

As soon as I receive Roberts OLD (hehe) Mic & A/D,
I plan on doing some comparisons using an OLD 300Mhz O-Scope, and then borrow a 3GHz and if need be a 13GHz depending on the results I get!

I am a Time Domain Junkie, I will leave the Frequency domain stuff to Robert. I enjoy seeing, the Fireing pin hit the primer, the round exit the can, and the impact. :lol:

Open to ANY Ideas you folks have. eMails are GLADLY accepted!
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Post by Hush » Thu May 19, 2005 8:50 am

I'd say that your a man on the right track. :)

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o-scopes

Post by PCArms » Thu May 19, 2005 10:59 am

I just checked, the Agilent we have, DSO812304a is a 13GHz, 40GSa/s, and can measure rise times faster than 50 ps.

The Tektronix TDS6154C is a 15GHz, 40GSa/s sample rate and is able to measure 30ps rise/fall times!

Of course at those resolutions, :shock:
(and that which Robert is measuring and displaying)
it is difficult for the HUMAN EAR to distinguish.
But it looks really cool on paper, (or on the screen).
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Post by silencertalk » Thu May 19, 2005 11:18 am

You only need a rise time of 17.5 microseconds to cover the 20Khz human hearing range. Of course most of us cannot hear to 20 Khz.

0.35 / bandwidth = rise time.

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Post by Hush » Thu May 19, 2005 1:39 pm

Huh, what did you say? :) Well thats true, as we get older we lose some high frequencies, but maybe its because of gunfire, who wears hearing protection while hunting, weather shotgun or lowly .22rf, in time it all does some damage.
I'm sure if we look around we can find someone who has not been exposed to gunfire during their lifetime who can hear up past our range of hearing and its associated frenquncies, which is why we strive for the quietest supressor.
I also think it would be benificial to allow people to hunt with moderators, to protect ones hearing with a low enough report to save hearing.
JMO :)

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Re: Sound meters vs. O'scope

Post by William Perkins » Thu May 19, 2005 11:28 pm

Hush wrote:Might I suggest something which I do not see anyone referring to here and that is an ocilloscope. . . appears on the scope so that it may be photographed.
Actually that is not a new idea. The 1968 report "Silencers, Principles and Evaluations" from the Army Frankford Arsenal used a Techtronix oscilloscope with an Altec 1/2" condenser microphone and a Brul and Kjaer 1/4" mic. To quote from the book, "Throughout the tests the microphone, preamplifier, recording equipment and recording technique were found to have a paramount effect on the validity of recorded sound data." Duh. The problem is that the oscilloscope might be perfectly accurate but if the microphone or preamp aren't up to the job the data will be invalid. I think that technology has marched past the days of the oscilloscope.

“A kind word and a gun will get you more than just a kind word.”
Al Capone

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Post by Hush » Fri May 20, 2005 8:26 am

Perhaps, I admit its been years since I worked in the field and I've missed much.
But whats so wrong with it if it works?
I'm sure much better equipment has come down the pike, I certainly hope so.
I guess its a matter of what a person likes, I like to see a trace and point and say ah, here is the hammer fall, etc.
Again I don't know what modern marvels are on the market today, but I'm not a snob, show me a new piece of gear and the chances are I'll love it.
Anything to make the job easier. :)

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Post by PCArms » Fri May 20, 2005 8:37 am

AGREED,

in the TIME DOMAIN, you can compare different actions,
like say, 10/22 vs 77/22 to see semi vs bolt action.
Also to see if the higher peeks are happening as the projectile exits the barrel, or the impact.

I am NOT putting down Roberts work in ANY WAY, just like to see things in many different ways. :!: :!: :!:
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Post by Hush » Fri May 20, 2005 10:07 am

PCArms wrote:AGREED,

in the TIME DOMAIN, you can compare different actions,
like say, 10/22 vs 77/22 to see semi vs bolt action.
Also to see if the higher peeks are happening as the projectile exits the barrel, or the impact.

I am NOT putting down Roberts work in ANY WAY, just like to see things in many different ways. :!: :!: :!:
Thats exactly what I'm saying. keep an open mind.
There's always something new to learn, something that may help or not.
Nothing wrong with thinking "outside the box" so to speak.
Thing have come far from when I first got interested in supressors, back then it was flat baffles and their spacing, trying different baffle shapes, Mickey Finn's K baffles which are still popular, now there are ceramics, different heat absorbing materials besides rolled up alum. screening, plain, oiled or greased, along with slanted flat baffles.
The tech stuff I know is old tech and I'm the first to admit it, this is why I'm here, to play catch up, I want to see the new baffle designs, I want to learn about new heat absorbtion materials and technology.
This dog ain't that old I can't learn a new trick or two. :)

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