On Mon, Jun 03, 2013 at 08:10:59PM +0300, Sampo Syreeni wrote: > >2) Will using some filters help to achieve this ? > > Here I'm not too sure yet. If you look at e.g. > dafx04.na.infn.it/WebProc/Proc/P_250.pdf , on the WFS > side they seem to be including frequency dependent terms for > the correction as well.
Note the sqrt(k) factor in eq.(4). This the 3dB/oct factor I mentioned before. It arises because in the derivation of the driving function vertical line sources are replaced by point sources, and NOT because the resulting line array of secondary sources behaves as a line source. So even if a very high order 2D AMB arrary looks just the same, it does not need those filters, and in WFS they are not there in order to obtain more 'plane' waves, but to have a flat frequency response of the system as a whole. And if you would build a full 3D WFS system (i.e. covering an entire enclosing surface with monopole secondary sources), these filters _do not go away_. Rather, they would be 6dB/oct in that case. Another way to see this is that the monopole secondary sources need to be driven by the projection of the gradient of the field on the normal of the enclosing surface, and pressure and gradient magnitude have this 6dB/oct relation. Again, no such filtering is required for 3D Ambisonics. There is no similarity at this level between AMB and WFS, because even if the speaker arrays can be the same they are being driven in an entirely different way. The two systems do _not_ converge in the limit. Ciao, -- 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 [email protected] https://mail.music.vt.edu/mailman/listinfo/sursound
