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Klippel Near Field Scanner on a Shoestring
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Old 12th January 2019, 07:29 PM   #521
gedlee is offline gedlee  United States
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Originally Posted by scott wurcer View Post
Good to know I'm not the only one (69 in two weeks). My sister took me to the Tiffany museum Winterpark FL the restoration of the chapel from the World's Fair is worth seeing.
I've seen it. The best display is in NY at the Historical Museum.
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Old 13th January 2019, 05:47 AM   #522
Dave Zan is online now Dave Zan  Australia
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I don't see how FEM/BEM would aid in this task in any way...
It's not for this task, it's just a new machine with sufficient speed for BEM.
So it should have more than ample speed for any plausible calculations on this task.

Best wishes
David
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Old 15th January 2019, 07:38 PM   #523
Ezcl is offline Ezcl  United States
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Originally Posted by gedlee View Post
How one gets the impulse response is not critical, although some methods are better than others, and some programs will output an array of data - as required - and others won't. I built my software around HolmImpulse and it works very well, but any means of getting a single file with the impulse responses at various angles will work.

As to myself, ...

My intention is to get back to this, but my circumstances are not making that easy.

...
Sounds good to me, and that's certainly understandable - I'm fairly certain we all have more things we'd like to do than we are able, no matter our age.

I ask about the data format because I have built a tool that automates polar measurements at work, and I'd love to spit out the correct format for use in this tool. Is there an example of the proper data somewhere in this thread? If not, could one be posted so I can follow it?
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Old 15th January 2019, 09:19 PM   #524
3ll3d00d is offline 3ll3d00d  United Kingdom
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Originally Posted by Ezcl View Post
I ask about the data format because I have built a tool that automates polar measurements at work, and I'd love to spit out the correct format for use in this tool. Is there an example of the proper data somewhere in this thread? If not, could one be posted so I can follow it?
I added the commonly available formats and mostly added some comments to explain the format, for the most part this means expecting a directory full of files which are named according to the angle they represent and that contain data in some known format. The supported formats being

- wav
- dbl
- ARTA PIR
- REW txt format

There is then the HolmImpulse export format which is described in pypolarmap/load.py at master * 3ll3d00d/pypolarmap * GitHub

This is a semi colon delimited format where the angles have been embedded in the header (aka the measurement names) as a convention
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Old 1st February 2019, 04:48 PM   #525
gedlee is offline gedlee  United States
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I have concluded that I am the wrong person to be key in moving this software along. So consistent with what I said at the beginning, I will make all the code that I have available so that perhaps someone else can move the numerical code along.

This code is in FORTRAN and compiles on the INtel compiler under Visual Studio.

I am not sure how to post it, any ideas? I'd prefer for someone to take this on and then I would work directly with them rather than just posting the coed in the public domain.
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Old 1st February 2019, 11:25 PM   #526
Dave Zan is online now Dave Zan  Australia
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I have been in touch with Prof. Weinreich...[re] my ideas for room reflection reduction...stationary microphone. Time will tell!
So, before you pass the torch, what did time tell?
I assume you would have mentioned if you had been successful, have you reached any conclusions?

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David
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Old 2nd February 2019, 05:50 PM   #527
gedlee is offline gedlee  United States
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I meant to comment on that.

The discussions were not very fruitful owing to the fact that he is well over 90 and I'm almost 70. We just did not seem to be able to communicate very well via E-mail.

I have concluded however that all two layer measurements are basically equivalent. What one is doing is measuring the radial velocity rather than the pressure, which will be highly robust to external reflections. The radiation is then expanded in terms of the radial velocity modes instead of the pressure. This can be done with a rotating source just as well as a stationary one. It just requires an intensity type of measurement using the pressure gradient rather than the pressure. A small modification would be required in the math, but nothing complicated.
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Old 3rd February 2019, 08:38 PM   #528
kessito is offline kessito  Netherlands
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Hi all,

For everyone wanting to understand the topic better, I just found this thesis which is very thorough and well written and a great source of information I think. ( though it might take quite some time t really understand it)
Cheers, Kees

Near-field acoustic holography with sound pressure and particle velocity measurements - Microflown
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Old 3rd February 2019, 09:55 PM   #529
gedlee is offline gedlee  United States
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Thanks Kessito

A highly theoretical coverage of the subject. Jay Maynard, Earl Williams and Eugen Scudryk were all contemporaries of mine at Penn State. This is how I learned these fundamental techniques. But for our purposes - simplicity - I don't think this kind of intense theory is really an advantage. Makes for a good thesis, but not good background for a simple and effective method.
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Old 4th February 2019, 12:15 AM   #530
mwmkravchenko is offline mwmkravchenko  Canada
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Klippel Near Field Scanner on a Shoestring
Still watching. I can do polar measurements and computation with a few programs. My SpeakerTesterPro does it well, and ARTA can do a good job of it. This PyPolar program offers options not available in either. If I can help in my limited time in between either projects or keeping the bills paid I'm willing to aid and abet!
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