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Recording peak amplitude of muzzle blast

A

amdx

Jan 1, 1970
0
Hi All,
I would like to setup 5 microphones to record the peak
amplitude of a muzzle blast, N,S,E,W, and above.
All I need are relative measurements to compare against each other.
I want to do this a very low cash outlay. I will build a peak
detector/sample hold for each mic.
I'm thinking of using the WM-61A mic.
http://search.digikey.com/scripts/DkSearch/dksus.dll?Detail?name=P9925-ND
The mics will be placed within 4ft of the muzzle,
Do I need to place some type of mechanical attenuator around the mics?
How would you suggest doing that?
Regarding the peak detector, sample and hold, display.
Easy part first, Display- use existing DVM, maybe with a 5 position switch
to
select held data from mics.
Looking for peak detector and sample/hold ideas, or if there is another
method?
Have good stock of transistors and some basic ICs.
Cost is important.
Thanks, Mike
 
x-no-archive:
 I would like to setup 5 microphones to record the peak
amplitude of a muzzle blast, N,S,E,W, and above.
 All I need are relative measurements to compare against each other.
I want to do this a very low cash outlay. I will build a peak
detector/sample hold for each mic.
I'm thinking of using the WM-61A mic.
 http://search.digikey.com/scripts/DkSearch/dksus.dll?Detail?name=P992...
The mics will be placed within 4ft of the muzzle,
Do I need to place some type of mechanical attenuator around the mics?
How would you suggest doing that?
Regarding the peak detector, sample and hold, display.
Easy part first, Display- use existing DVM, maybe with a 5 position switch
to
select held data from mics.
Looking for peak detector and sample/hold ideas, or if there is another
method?
Have good stock of transistors and some basic ICs.
 Cost is important.
                Thanks, Mike

I have 3 suggestions for you:


1) consider RECORDING the the signals and analyzing them off line..
I think you will want to look at the waveforms, maybe apply some
filters etc etc, not just get a single NUMBER number from a DVM.
Once you have a recording of the signals you will be able to analyze
them in many interesting ways that you will think of..

2) yes you probably need an mechanical attenuator or use a mic that
will not clip at high SPL levels.

3) ask your question over at rec.audio.pro

Mark
 
G

GregS

Jan 1, 1970
0
Hi All,
I would like to setup 5 microphones to record the peak
amplitude of a muzzle blast, N,S,E,W, and above.
All I need are relative measurements to compare against each other.
I want to do this a very low cash outlay. I will build a peak
detector/sample hold for each mic.
I'm thinking of using the WM-61A mic.
http://search.digikey.com/scripts/DkSearch/dksus.dll?Detail?name=P9925-ND
The mics will be placed within 4ft of the muzzle,
Do I need to place some type of mechanical attenuator around the mics?
How would you suggest doing that?
Regarding the peak detector, sample and hold, display.
Easy part first, Display- use existing DVM, maybe with a 5 position switch
to
select held data from mics.
Looking for peak detector and sample/hold ideas, or if there is another
method?
Have good stock of transistors and some basic ICs.
Cost is important.
Thanks, Mike

Those will definately have a limitation. You can get better performance
from them by modifying them and of course, using maximum applied voltage.

I would ask rec.audio.pro

A mechanical attenuator might be too variable. I am getting maximum SPL of 120 -130
in some reading. There might be a method to increase the maxim rating by
using different resistors. I don't have the answer off hand, but anyway a link to my
microphone page...
http://www.pitt.edu/~szekeres/mic/mic.htm

greg
 
G

GregS

Jan 1, 1970
0
I severely doubt the effectiveness of putting 47nF mylar in parallel
with 6.8uF tantalum for audio in this circuit.
You must be an audiophool.

Now, for fun, try to calculate the impedance of 47nF at 20kHz.
It is 1 / j.w.C, where 'w' stands for Omega = 2 x PI x f,
or without the complex part 1 / 6.28 x 20 000 x 47 x 10^-9,
makes 100 000 / (6.28 x 2 x 47) = 169 Ohm.
At lower frequencies it will be much higher.

Tantalum caps have very low ESR in the milli Ohms range at that frequency.
http://www2.electronicproducts.com/Tiny_tantalum_chip_cap_achieves_4-mO_ESR-ar
ticle-xhlrr06-jun2006-html.aspx
Your circuit impedances are also in the several hundred Ohm region.
Those mylar caps do NOTHING.

Pretty much why I said not criticle.
Stop posting from an EDU, it makes the EDU look ridiculous.

I stopped reading your site there, as this shows you do not know what you are
doing.

Who cares
El Pante.

Your very right for comments about those caps. Its nothing more
than a reprint from an article done way back. 3rd month of 1985 Speaker Builder Magazine.
The caps are generic, and only specified for the people who might think they are necessary,
and when you mix and match, who knows what they are going to use anyway.

greg
 
A

amdx

Jan 1, 1970
0
There is no spec for maximum level, but it is probably about 130dB (if
you are lucky). To record peak level from the gun, it will need to be
good for about 170dB. 40dB of attenuation is probably not easy to
find, but a quick and easy way to get you somewhere near would be to
peel off the felt cover and put a blob of glue over the sound hole.
These capsules are cheap, so buy more than you need so you can
experiment.

For peak detection, how about using a laptop and sound card with four
inputs? You can then record the sounds and perhaps do more with them
later.

d
 
A

amdx

Jan 1, 1970
0
Sorry about the empty post.
Regarding the laptop, I didn't think it would sample fast enough
to make sure I get the peak of each pulse.
Expand more on that if you think it's fast enough.
Thanks, Mike
 
G

GregS

Jan 1, 1970
0
Sorry about the empty post.
Regarding the laptop, I didn't think it would sample fast enough
to make sure I get the peak of each pulse.
Expand more on that if you think it's fast enough.
Thanks, Mike

It would be determined by the AD stage, stages, speeds and memory.
I did have the idea of sampling also with one additional mike, attenuated and
distanced for a linear comparison.

I think using a dynamic mic is what you will need.

greg
 
G

GregS

Jan 1, 1970
0
So, so also have to lookup the meaning of critical:
http://www.merriam-webster.com/dictionary/critical

I'd say: It is not needed at all.

The essence is, is that learning, in this society, is often parroting
something, like chanting '1+1 makes 2' etc...
When you start _designing_, or being in any way creative other then repeating,
that no longer works.

We should have more understanding and less copy-cat.
In this specific case it would save 2 capacitors multiplied by the number of
people
who actually build that circuit.
The world would be greener ....
LOL

Around that time the goverment in the US took off the MPG yearly requirments
to improve the economy to increase sales and make big SUV's.
It made green money. They were thinking the wrong kind of green.


greg
 
D

Don Pearce

Jan 1, 1970
0
Sorry about the empty post.
Regarding the laptop, I didn't think it would sample fast enough
to make sure I get the peak of each pulse.
Expand more on that if you think it's fast enough.
Thanks, Mike

It will certainly sample fast enough to record the output of a
microphone - which is after all designed for the audio band. The peak
of the muzzle blast lasts about 5 milliseconds, which will contain
about 200 samples using a standard sound card. That is plenty.

d
 
J

Joerg

Jan 1, 1970
0
amdx said:
Sorry about the empty post.
Regarding the laptop, I didn't think it would sample fast enough
to make sure I get the peak of each pulse.
Expand more on that if you think it's fast enough.
Thanks, Mike

You'd need more channels. But read the fine print when shopping, many
USB sound cards can output six channels or so but may only have two
input channels.
 
B

BobG

Jan 1, 1970
0
Its hard to record hi spl without clipping the mic capsule. You
definitely need acoustic attenuation before the capsule. Eletrical
attenuation on the output of the mic just turns down the clipped
signal from the element. I'd say 4ft is too close. You're going to get
140dB four feet from the muzzle. Maybe put the mics in those 20dB
earmuffs they use in the gun ranges?
 
G

GregS

Jan 1, 1970
0
Hi All,
I would like to setup 5 microphones to record the peak
amplitude of a muzzle blast, N,S,E,W, and above.
All I need are relative measurements to compare against each other.
I want to do this a very low cash outlay. I will build a peak
detector/sample hold for each mic.
I'm thinking of using the WM-61A mic.
http://search.digikey.com/scripts/DkSearch/dksus.dll?Detail?name=P9925-ND
The mics will be placed within 4ft of the muzzle,
Do I need to place some type of mechanical attenuator around the mics?
How would you suggest doing that?
Regarding the peak detector, sample and hold, display.
Easy part first, Display- use existing DVM, maybe with a 5 position switch
to
select held data from mics.
Looking for peak detector and sample/hold ideas, or if there is another
method?
Have good stock of transistors and some basic ICs.
Cost is important.
Thanks, Mike

After thinking dynamic microphone so far I dug up this. I don't think you will
need any other amplifier.
http://www.mouser.com/Search/ProductDetail.aspx?qs=sGAEpiMZZMsYQxPYEnGVuLJZuW8Wb6%2bkxlI5RpqXChs=
 
D

Don Pearce

Jan 1, 1970
0
Its hard to record hi spl without clipping the mic capsule. You
definitely need acoustic attenuation before the capsule. Eletrical
attenuation on the output of the mic just turns down the clipped
signal from the element. I'd say 4ft is too close. You're going to get
140dB four feet from the muzzle. Maybe put the mics in those 20dB
earmuffs they use in the gun ranges?

140 is way low - you get almost that off a titanium faced golf club.
170dB must be considered an absolute minimum for a gun.

d
 
J

Joerg

Jan 1, 1970
0
Dynamic mikes can saturate quickly, big time. BTDT.
There are also some speakers you can use, or many speakers of 32 ohm or 100 ohm types.
They need a baffle of sorts.

This is actually a good idea. Maybe one of those piezo tweeters.
Probably in this application even a simple ceramic capacitor could
suffice as a sensing device.

Problem with all that sound attenuation material is that rot or mold can
set in quickly if this stuff is used outdoors.
 
A

amdx

Jan 1, 1970
0
Don Pearce said:
It will certainly sample fast enough to record the output of a
microphone - which is after all designed for the audio band. The peak
of the muzzle blast lasts about 5 milliseconds, which will contain
about 200 samples using a standard sound card. That is plenty.

d

I'm finding the initial peak is from 100usec to 800usec long, from 0 to peak
to 0.
I don't think I could ever be sure I caught the peak.
What do you think?
Mike
 
D

Don Pearce

Jan 1, 1970
0
I'm finding the initial peak is from 100usec to 800usec long, from 0 to peak
to 0.
I don't think I could ever be sure I caught the peak.
What do you think?
Mike

Possible - depends on barrel length and charge design. If you record
with a laptop, you can be sure you have the peak - otherwise you are
pretty much in the lap of the gods.

You do know this work has all been done in great depth - do you really
need to repeat it for yourself?.

d
 
J

Joerg

Jan 1, 1970
0
amdx said:
I'm finding the initial peak is from 100usec to 800usec long, from 0 to peak
to 0.
I don't think I could ever be sure I caught the peak.
What do you think?
Mike

If the sound card can sample 96k/sec or 192k/sec you should not have a
problem. Problem is you need to find one with five simultaneous inputs
and that will have to be an external one.
 
R

Rich Grise

Jan 1, 1970
0
I would like to setup 5 microphones to record the peak
amplitude of a muzzle blast, N,S,E,W, and above.
All I need are relative measurements to compare against each other.
I want to do this a very low cash outlay. I will build a peak
detector/sample hold for each mic.
I'm thinking of using the WM-61A mic.
http://search.digikey.com/scripts/DkSearch/dksus.dll?Detail?name=P9925-ND
The mics will be placed within 4ft of the muzzle,
Do I need to place some type of mechanical attenuator around the mics?
How would you suggest doing that?
Regarding the peak detector, sample and hold, display.
Easy part first, Display- use existing DVM, maybe with a 5 position switch
to
select held data from mics.
Looking for peak detector and sample/hold ideas, or if there is another
method?
Have good stock of transistors and some basic ICs.
Cost is important.

http://www.google.com/search?q=peak-detector

Have Fun!
Rich
 
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