Hi Steven, as Fons mentioned before such an array will have trouble to deliver proper HOA components at a useful range. Running a simple simulation here for R=17cm and assuming perfect matched microphones and perfectly (uniformly) arranged, spatial aliasing starts to become serious at 4.5kHz. Assuming that the encoding filters allow some noise amplification, eg 15dB, to get some more usable low frequencies: 2nd order is well behaved at 200 Hz - 5.5 kHz 3rd order at 600 Hz - 5 kHz 4th order at 1 kHz - 4.5 kHz 5th order at 1.5kHz - 4 kHz Since the microphones will have some unidealities, and their placement is not uniform as far as I can see, the actual performance can be worse than that, depending how much the encoding filters are optimized for the setup or not. And again that’s assuming 15dB of more noise (frequency-dependent) at the HOA signals than the microphones, which may be a problem at many recordings. Less permitted noise on the other hand means that all the low limits for all orders go up, hence, even smaller usable ranges.
If one wishes to capture spatial sound in a HOA format, instead of having a device that tries to do everything, it would make more sense to have a separate camera, and a dedicated HOA microphone since it requires careful optimization for that purpose. Regards, Archontis Politis > On 27 May 2017, at 23:47, Steven Boardman <boardroomout...@gmail.com> wrote: > > Surprise suprise, they can't provide a 3rd order sample at this point in > time.... > > Here is the message. > > "We talked with our R&D team regarding to the schedule of audio. As our > timeline is to achieve the 3rd order Ambisonic in first shipment in > October, from now to October we still have a lot of work to do. The 3rd > order Ambisonic is not ready yet. > > Right now our priority is the KickStarter, frankly speaking, we do not have > more personnel to optimize the recording. However, we have officially put > forward the needs of the 3rd order Ambisonic, and R&D team will prioritize > it. > > We will try our best to give you a demo before the KS ends. However, if we > can't do it, we will update you as soon as it comes out." > > On 26 May 2017 20:15, "Fons Adriaensen" <f...@linuxaudio.org> wrote: > >> On Fri, May 26, 2017 at 04:29:02PM +0100, Steven Boardman wrote: >> >>> ‘Yes, 3rd Ambisonic will be in the first shipment, but 5th order >>> Ambisonic rendering will be provided in the early next year, by >>> upgrading the software.’ >> >> Anyone promising usable 5th order from such a system is either >> ignorant or deliberately misleading potential customers. Typical >> kickstarter vaporware. >> >>> A sphere of 17cm can’t be that great at high freq? >> >> Depends on the distance between the capsules. In this case the >> diameter is twice that of the Eigenmic, and the number of capsules >> is doubled, so polar patterns will start to break down at around >> 6 to 7 kHz or so (assuming optimum capsules placement). >> >>> Especially as the spec for each mems capsule is: noise level 67db, >> >> Let's hope they mean a S/N ratio 67 dB, which is a self noise level >> of 27 dB :-) >> >> Ciao, >> >> -- >> FA >> >> A world of exhaustive, reliable metadata would be an utopia. >> It's also a pipe-dream, founded on self-delusion, nerd hubris >> and hysterically inflated market opportunities. (Cory Doctorow) >> >> _______________________________________________ >> Sursound mailing list >> Sursound@music.vt.edu >> https://mail.music.vt.edu/mailman/listinfo/sursound - unsubscribe here, >> edit account or options, view archives and so on. >> > -------------- next part -------------- > An HTML attachment was scrubbed... > URL: > <https://mail.music.vt.edu/mailman/private/sursound/attachments/20170527/045f7833/attachment.html> > _______________________________________________ > Sursound mailing list > Sursound@music.vt.edu > https://mail.music.vt.edu/mailman/listinfo/sursound - unsubscribe here, edit > account or options, view archives and so on. _______________________________________________ Sursound mailing list Sursound@music.vt.edu https://mail.music.vt.edu/mailman/listinfo/sursound - unsubscribe here, edit account or options, view archives and so on.
