Hello Garth, Dave, I'd advise converting from B-format to A-format, then doing all de-noising, compression, etc, in A-format. Followed by, re-encoding back to B-format.
This is how I've done all my work (both acousmatic involving field-recordings and musical location recordings). Depending on your de-noiser / gating settings, you can get image distortion effects... but these are similar to working with stereo. If you really want to be precious, instead of just 4 channels of A-format (for FOA), you can decode to more (say 6 channels as vertices of an octahedron, or 8 channels, in a cube), do your processing and then re-encode back to B-format. Also, you can adjust the polar patterns of your decode. Using 'controlled-opposites' decode can give you a smoother result, depending on your material. If you use a more custom version of A-format (octahedron or cube), make sure your re-encoding matrix is correctly scaled, so you get the correct balance of W vs X,Y,Z on re-encoding. Hope this helps! My best, ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Joseph Anderson j.ander...@ambisonictoolkit.net http://www.ambisonictoolkit.net ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ On 5 Aug 2014, at 4:09 am, Dave Malham <dave.mal...@york.ac.uk> wrote: > Hi Garth, > An interesting one. certainly got me thinking - trouble is, you don't > really want thoughts but measurements. I suspect it depends a lot on what > the internal mechanism of the noise reduction system is. Mostly, as far as > I can ascertain, there's an analysis filter bank to split the sound into > bands which are then subject to some sort of processing, then the bands are > re-combined somehow either directly or by resynthesis to produce the > output. The most critical thing will usually be the combination of the > analysis and resynthesis steps. For instance, a well designed and well > implemented FFT/iFFT pair should preserve the phase well. However, since > you rarely have access to the internals of these things for analysis, > measurement - or just listening with a good pair of ears - is the only way > forward. > > I suspect that processing the B format after conversion from A would be the > best - anyone else have any thoughts? > > Dave > > PS Of course, you could just always process the speaker feeds, for know, as > that would be the least risky but most processing heavy option > > > On 4 August 2014 20:23, Garth Paine <ga...@activatedspace.com> wrote: > >> Hi everyone >> >> I have been doing a lot of ambient Ambisonic A format recordings (sps200 >> into SD788) and as the environmental levels are so low the self noise of >> the microphone becomes a bit of an issue on playback - I have RX for stereo >> noise reduction but have not found a solution for multichannel that would >> make me relaxed about maintaining the phase for decoding - I want to output >> B-Format so decoding onto any speaker array rather than just output 5.1 and >> use a surround noise cleaner. I would appreciate thoughts from the list - >> I am guessing as the Soundfield mics are know for self noise that others >> have faced and perhaps solved this issue already? thanks in advance >> >> ps. you can hear some of the recordings here >> http://listen.ame.asu.edu/sonic_events.php >> >> Cheers, >> Garth Paine >> ga...@activatedspace.com >> >> >> -------------- next part -------------- >> An HTML attachment was scrubbed... >> URL: < >> https://mail.music.vt.edu/mailman/private/sursound/attachments/20140804/ca2c4e9f/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. >> > > > > -- > > As of 1st October 2012, I have retired from the University. > > These are my own views and may or may not be shared by the University > > Dave Malham > Honorary Fellow, Department of Music > The University of York > York YO10 5DD > UK > > 'Ambisonics - Component Imaging for Audio' > -------------- next part -------------- > An HTML attachment was scrubbed... > URL: > <https://mail.music.vt.edu/mailman/private/sursound/attachments/20140805/d6cb70e1/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. -------------- next part -------------- An HTML attachment was scrubbed... URL: <https://mail.music.vt.edu/mailman/private/sursound/attachments/20140805/26eef386/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.
