Re: [Sursound] RIR measuring, how to capture a higher order Ambisonic room responce?
On 04/29/2018 06:13 AM, Dave Malham wrote: Excellent - this is exactly the method I was about to suggest - steppers, related hardware and motor control boards have been driven down in price so much by the 3-d printing/cnc/maker revolution that it makes almost no sense to do anything else. Yes, I like that too... I was planning on adding a stepper and gear drive to my test rig (I turn it manually, not too hard). This would have been fine for tetrahedral microphones and horizontal plane only measurements. The problem for me surfaced when I went to second order microphones and needed measurements above and below the horizontal plane. I built a "better" test rig that can tilt, added a small xy table to be able to "calibrate" the center of rotation (and of course 3d printed a fixture to attach the mic!), but I need to physically reposition the rig between each layer being measured. Not the best. I was going for a different approach when it was suggested to me (both by my boss and a phd student here, thanks Chris & Elliot) that a robotic arm would be better and more general purpose. I was reluctant because of the cost... (a bit off topic but maybe of interest anyway) I was actually going to use a telescope mount (_not_ an equatorial mount which are the most common, apparently), I found one that would do what I needed, was not expensive, and I could control azimuth and elevation through rs232 (SkyWatcher AllView). I designed (on paper :-) a pantograph that would keep the microphone away from the mount, and replicate the movements. But again, lots of mechanical parts and tricky design. Better to spend time on the microphones. So I bought a robotic arm. Len (from Core Sound) asked off-list about it, so I'm including some information here. I got the WidowXL from Trossen Robotics. Anything better (as far as I could find, not an expert!) would have driven the price up exponentially - this one is not cheap anyway. I just spent two full days assembling it (lots of pieces, lots of screws). Beware, ask before you buy as to delivery times - mine was delayed several times and they were not very upfront about it (or just did not know). Anyway, I just did some preliminary tests today and it seems to be able to hold my microphone and move all the joints so as to point it in the right directions and rotate it accurately. Lots to do, but it is a start (to get better data). -- Fernando I would use the esp8266 arduino compatible wifi module which costs about the same as a decent cappuccino - I paid about 4 euros for one at the end of last year - which has a reasonably powerful 16 bit processor and is quite capable of acting as a web server, so I'm doing that and controlling my steppers from a web based interface on my mobile or laptop. Note, however, that I've confined it to just my home network for security sake - don't want people using it to influence the elections :-) Dave PS Sorry once again I'm not currently doing this for audio - maybe one of these days I'll get back to that. On 24 April 2018 at 02:58, umashankar manthravadiwrote: I have been using a stepper motor (of the kind used in 3d printer ) driven by a low cost Arduino and motor control board. I 3d print a snug fitting fixture for the microphone with the motor shaft aligned to the array centre. ___ 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.
Re: [Sursound] Strange 'buzz' in Ambisonic recording
I suspect that depending of chosen virtual mic configuration there is so much low frequency gain added that you boost the level of the nearly always existing 50Hz hum so much that you actually hear it. It has sometimes happened to me that I need to lower the input level of the signal to the ambisonic decoder otherwise i got signal clipping in the processing stage. BR Bo-Erik 2018-05-07 18:30 GMT+02:00 Gerard Lardner <glard...@iol.ie>: > I'm very much an amateur here, so please forgive what might be a stupid > question! > > I recorded a concert on Saturday (John Rutter's /Gloria /and Karl Jenkins' > /The Peacemakers/) using an Ambisonic mic and some others. I'm encoding the > A-format to B-format using VVEncode in Reaper, and panning in the extra > mics using Wigware Ambipan. The result is then decoded to surround sound or > to stereo using VVDecode; all in the same Reaper set-up. I've used this > approach before, usually successfully. > > I find that, when the organ and brass are playing at full volume (I mean > in the orchestra, not just in playback), there is a 'buzzing' sound in the > playback. It sounds harsh, pitched at about 50 Hz. But if I listen to the > A-format files alone in Reaper or in VLC Media Player, there is no buzz. > Similarly, there is no buzz if I encode the A-format using the stand-alone > version of VVMic. The buzz is present both in the B-format from the > Ambisonic mic and, less strongly, in the panned B-format from the soloists > mic. It appears to be an artefact of my editing configuration; but it > didn't happen in a recording I made, using the same configuration, last > month. The only difference since then has been that my old hard disc, which > had developed some faults, was cloned onto a new SSD. > > Does this description suggest a specific problem/remedy to anyone? I know > I can produce a decent CD using the stand-alone VVMic route and panning in > the soloists into the stereo mix; but I'd like to get to the bottom of why > my Ambisonic configuration is doing this now. > > -- next part -- > An HTML attachment was scrubbed... > URL: <https://mail.music.vt.edu/mailman/private/sursound/attachme > nts/20180507/fffd5727/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/20180507/d2a3faae/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] Strange 'buzz' in Ambisonic recording
I'm very much an amateur here, so please forgive what might be a stupid question! I recorded a concert on Saturday (John Rutter's /Gloria /and Karl Jenkins' /The Peacemakers/) using an Ambisonic mic and some others. I'm encoding the A-format to B-format using VVEncode in Reaper, and panning in the extra mics using Wigware Ambipan. The result is then decoded to surround sound or to stereo using VVDecode; all in the same Reaper set-up. I've used this approach before, usually successfully. I find that, when the organ and brass are playing at full volume (I mean in the orchestra, not just in playback), there is a 'buzzing' sound in the playback. It sounds harsh, pitched at about 50 Hz. But if I listen to the A-format files alone in Reaper or in VLC Media Player, there is no buzz. Similarly, there is no buzz if I encode the A-format using the stand-alone version of VVMic. The buzz is present both in the B-format from the Ambisonic mic and, less strongly, in the panned B-format from the soloists mic. It appears to be an artefact of my editing configuration; but it didn't happen in a recording I made, using the same configuration, last month. The only difference since then has been that my old hard disc, which had developed some faults, was cloned onto a new SSD. Does this description suggest a specific problem/remedy to anyone? I know I can produce a decent CD using the stand-alone VVMic route and panning in the soloists into the stereo mix; but I'd like to get to the bottom of why my Ambisonic configuration is doing this now. -- next part -- An HTML attachment was scrubbed... URL: <https://mail.music.vt.edu/mailman/private/sursound/attachments/20180507/fffd5727/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.