Hi Dave Nice to hear from you and thanks for your input - it seems strange to me, given the known self noise of the most prevalent ambisonic microphones that there is not a solution out there already. Indeed your summations of the process aligns with mine, but I am somewhat nervous about looking to apply this over all 4 channels as there is so little across the 4 channels that I could use as a common measure of phase accuracy after processing, and to be honest I am not looking to write code for this as DSP is not my strong point - but I would see a use for this across the community.
I would of course be happy to apply the noise reduction to the B-Format file. The idea for the Listen(n) project is to provide a wind range of listening outcomes from mobile devices with headphones to surround sound setups - so the decoding would need to be simple and be applicable across domestic platforms - so I am imagining that the noise reduction would therefore need to happen pre decoding to the listening format? Would love to find a solution - It has been suggested for instance that I use single instances of Izotopes RX on each of the 4 channels for the A-Format file and load a noise template in each - still I am concerned about any phase variation pre to decoding. Am I being over concerned? Cheers, Garth On Aug 5, 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. _______________________________________________ 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.
