Hi Steven, (hurried reply on the go) the numbers were for 17cm diameter (8.5cm radius). You also get around 15-18dB SNR improvement just by combining that many microphones, that’s still included in that simulation.
I wasn’t saying that the device is not good or useful, apart from the video, you can do a lot of useful stuff with that many microphones, binaural rendering, beamforming etc.. I was saying that it’s not a very good HOA microphone with these specs. Best, Archontis Politis On 30 May 2017, at 16:26, Steven Boardman <boardroomout...@gmail.com<mailto:boardroomout...@gmail.com>> wrote: Hi Archontis The size is 170mm diameter not radius. They also state the capsules are in arrays of 16, so 4 arrays of 16 capsules. Looking at the camera though, I can’t work it out…. The also said: 'The noise and frequency respond i quote is for individual mic. We have noise reduction algorithm to improve 15db in total compared to each mic. For frequency respond, we are using the EQL process，reach to the “flat".' I knew that it wouldn’t be well behaved in the entire range, and as a consequence could not be relied on for a quality full bandwidth recording. This isn’t always the point though. As it could still be used as a reliable reference for the most crucial of frequency ranges, the voice. As long as it can record dialogue, one can reconstruct with ADR. It’s just wether it is intelligible, and accurate enough spatially. 90% of audio for films is done in post anyway, especially dialogue. It includes 6 camera’s (and the footage isn’t too bad), so to me it seems like a bargain. I just need to hear the audio first. Otherwise it maybe better just to spend it all on a camera. What has been mentioned by Fons, and yourself is obviously completely true, but we all know in practice it is probably worse. Even more reason to hear their 3rd order render. Of course 5th is a dream….. While we are on the maths; For 3rd order, and with the minimum amount of capsules, how small would the sphere need to be, for a range up to say 16kHz, or maybe even 18kHz? Am I correct in assuming that the distance between the capsules needs to be less than half the highest wavelength represented? Best Steve On 27 May 2017, at 23:18, Politis Archontis <archontis.poli...@aalto.fi<mailto:archontis.poli...@aalto.fi>> wrote: 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 -------------- next part -------------- An HTML attachment was scrubbed... URL: <https://mail.music.vt.edu/mailman/private/sursound/attachments/20170530/43b87df5/attachment.html> _______________________________________________ Sursound mailing list Sursound@music.vt.edu<mailto: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/20170530/b80de9d5/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.
