Recording peak amplitude of muzzle blast

Have Fun! Rich

Have Fun! Rich

On a sunny day (Thu, 29 Jan 2009 20:57:21 GMT) it happened snipped-for-privacy@zekfrivolous.com (GregS) wrote in :

Then you can just as well use a small speaker as mike, like the ones in a small transistor radio. No amplifier needed either. :-)

Hope This Helps! Rich

What is this thing you call Google ? Mike

Well, I think they are better than electrets. I also thought about bimorphs and pressure sensors. I don't think piezos are that linear and sensors are typically slow. I'm getting search results of gifles and gunshot sounds from 140 dB to over 170. Here is a piece by Shure....

and pressure

The PZT-5H material we use is quite linear. I don't know much about audio ceramics but I don't think Mike needs this to be particularly linear, he just wants to find the peak timings.

170.

Quote: "In the 10 kHz range, 180 dB SPL is the MAX SPL of the SM58. However, this is a calculated measurement as Shure Engineering had no means to create such enormous and dangerous SPL."

Maybe they should hire an engineer who is a NRA member :-)

[...]

--
Regards, Joerg

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Just a clarification: I want to compare relative amplitude of different impulses. Mike

switch

and pressure

170.

As Joerg states, PZT ceramics are linear up to very high levels. In air, you'll have a natural attenuator due to the impedance mismatch. You also have good impulse response with ceramics. As for sampling, use a 4-channel digital oscilloscope. You can save all your results for post processing (best to save table of numbers than visuals).

--
Mark

Oh. Then it has to be linear and sound muffling will probably be out as well because moisture and whatnot will change its muffling performance.

You'll probably have to look into piezos and ceramic capacitors as mikes if it has to be cheap. Professional stuff like this will be pricey:

--
Regards, Joerg

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switch

and pressure

170.

DSOs offer poor dynamic range. 6 ENOBs if you are lucky, maybe around

35dB. My Instek here is a bit better but still nothing to write home about in terms of dynamic range. I'd go the sound card route where you can easily obtain >16 ENOBs on the cheap. If you can find one with five or more inputs, that is.

--
Regards, Joerg

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"amdx" wrote in news:31017$4981cfca$18d6b40c$ snipped-for-privacy@KNOLOGY.NET:

The sound levels producd by a muzzle blast are too high, and your WM-61A mics will go into hard clipping long before the peak pressure of the blast is even close to being reached. Miniature hydrophones would work, but they are expensive. The only low-cost solution of which I am aware would be dynamic pressure sensors such as those made by Endevco, Entran and Kulite. They too are expensive if purchased new, but can occasionally be purchased for pennies on the dollar on eBay. You will need to check the specs to make sure that the ones that you purchase have sufficient sensitivity and bandwidth, but at least they will not clip/overload. They are mostly strain guage type sensors, so you will need to build up appropriate signal condition circuitry in order to use them.

"GregS" Joerg

** Absolute bullshit.

Any dynamic mic worth the name will handle huge SPL levels.

** Very much better than low cost electret capsules.

...... Phil

?name=P9925-ND

Bruel & Kjaer is another manufacturer (the original) often found used on ebay, and BSWA Tech is a Chinese manufacturer of equivalent microphones at lower cost but still expensive and not much available used. For a reasonably accurate peak pressure measurement one of these solid metal diaphragm measurement microphones is the only real alternative, so it is a good thing that is not what the OP wants :-).

Even the best available measurement microphones cannot resolve the rise time of the shock wave from the muzzle blast of a supersonic round, thus missing the exact peak by a bit. Even custom microphones with 200 ns risetime to a shock wave can't do that, and getting even that slow (compared to actual shock) risetime requires having the bare microphone diaphragm mounted perpindicular to the direction of shock wave propogation quite accurately.

I like the piezo idea, calibrated for the same respone when placed in a small group equidistant from the muzzle, and checked at various distances for linearity assuming inverse square attenuation (neglecting losses) with no reflections involved - complete your measurement before the first reflection can reach the microphone.

[...]

Piezo material can take a huge punch. Some of the gear we designed had to ultrasound-image during lithotriptor shots (to pulverize kidney stones and such). That is like listening to a Mozart concerto next to an ordnance disposal pit. The main challenges are in the recipe and processing of the backing material.

Another option might be PVDF but I do not have experience how that fares in the audible range.

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I think at 44200khz sample rate sound cards sample every 23us.

That will get you 30 to 40 samples with a mediocre sampler and 60 to

80 with a better one. Plot them and look at the plots. Your eye will tell you.

?name=P9925-ND

A rather divergent idea: how about using a dynamic mike fed into a current amplifier? The resulting high damping because of the low input impedance might help keep the excursion within reasonable mechanical limits, as well as diminish the sensitivity of the mike enough that it might be able to handle the wave front (which I suppose resembles more of a soliton). Too crazy an idea?

carlos.

How about recording the muzzle flash instead of the muzzle blast?

Vladimir Vassilevsky DSP and Mixed Signal Design Consultant