Fernando Lopez-Lezcano wrote:




It is a bit frustrating to read about (probably)  interesting projects
which are< completely unintroduced >.

https://ccrma.stanford.edu/search/node/Octathingy

Didn't find any real info. Is this supposed to be some 2D design? If so,
Orange Research Labs also had some prototype, and also some 12-capsule
(2nd order-3D) prototype but which seems to be to big. (Capsule
distances on sphere implied an spatial aliasing limit of about 4.5kHz,
which would be (too) low for any serious recording.)

So, < before > talking about 3D printed holders: What actually IS an
8-capsule Octathingy?


Sorry about that, yes, the Octathingy is the informal name and it would not be found by a search. As I say, there is a LOT of documentation missing from the pages. I will slowly fix that, thanks for pointing this one out!

Waiting for some enlightening infos...     :-)


I have to add a link and/or the pdf of the paper. Look for the AES Audio Engineering Society Convention Paper 8728 (2012) by Eric Benjamin, "A second-order soundfield microphone with improved polar pattern shape"... the abstract says:

"The soundfield microphone is a compact tetrahedral array of four figure-of-eight microphones yielding four coincident virtual microphones; one omnidirectional and three orthogonal pressure gradient microphones. As described by Gerzon, above a limiting frequency approximated by f c = πc/r, the virtual microphones become progressively contaminated by higher-order spherical harmonics. To improve the high-frequency performance, either the array size must be substantially reduced or a new array geometry must be found. In the present work an array having nominally octahedral geometry is described. It samples the spherical harmonics in a natural way and yields horizontal virtual microphones up to second order having excellent horizontal polar patterns up to 20 kHz."

The capsules are located in the vertices of a square antiprism...

(the reference is also in the paper about the project that I have in my home page)
Best,
-- Fernando

Thank you very much for providing these detailed and useful pieces of informations!

Best,

Stefan
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