Hello Hector, > As quoted below, some time ago Fons kindly provided the equations to > extract virtual microphone signals from an ambisonic 1st order soundfield. > I was wondering, is there a set of available and known formulas to extract > virtual microphones from 2nd order recordings, taking advantage of the > higher spatial resolution?
If you want first order virtual mics you can use the same formulas, just drop the higher order signals. Note that the equations you quoted are for FuMa normalisation, higher order signal sets today would probably use SN3D. For SN3D, remove the sqrt(2) in the first equation. If you want 2nd or higher order virtual mics things get a bit more complicated. Of course any polar pattern is just a weighted sum of the AMB components. But for higher order you get a lot more choices. Now if you limit the choice to axisymmetric patterns things get easier. Axisymmetric polar patterns are those that depend only on the angle between the axis of the mic and the direction of the source, i.e. you can imagine the pattern as something that is rotated around an axis in a given direction. All first order patterns are axisymmetric, but higher order ones don't have to be. But even for axisymmetric higher order patterns you need more than some simple equations that I could copy into an mailing list post. I could sent you some python code that computes the gain factors for higher order axisymmetric virtual mics. Let me know if you're interested. Ciao, -- FA _______________________________________________ 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.
