On Sat, Dec 05, 2015 at 06:06:08PM +0000, Stefan Schreiber wrote: > Fons Adriaensen wrote: > > >* The hedgehog is at least twenty times as big. > > > Hardly...
Depends on which picture you look at, but OK, let's say ten times (see Fig.12). > > The OZO's will > > be omni over most of the frequency range and turn into > > something like subcardioid only at very frequencies > > (above 4 kHz or so). > > And how can/could you know this? Basic theory really. No matter what type of mic you place behind such a tiny hole, it will pick up the pressure at that tiny hole. So apart from diffraction effects the result will be omni. It's not too difficult to compute the diffraction caused by a solid sphere. You can see the resulting polar patterns for 16 cm diameter sphere here: <http://kokkinizita.linuxaudio.org/export/sphere16.pdf> Even if the OZO isn't exactly spherical, the results will be similar. It's also interesting to look at the result of taking the difference signal of two diametrically opposed capsules: <http://kokkinizita.linuxaudio.org/export/sphere16-diff.pdf> This produces a usable fig-8 up to 1 kHz or so (with lower frequencies requiring additional gain). Above that, chaos takes over. Using more mics (e.g. the four frontal ones minus the four at the back) will not improve things. Note that such a fig-8 pattern is a component of any first degree directional pattern and also of most higher degree ones. If can't be obtained then the same is true of any pattern of which it is a component. Caio, -- FA A world of exhaustive, reliable metadata would be an utopia. It's also a pipe-dream, founded on self-delusion, nerd hubris and hysterically inflated market opportunities. (Cory Doctorow) _______________________________________________ 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.
