On 2021-12-02, Jens Ahrens wrote:
It’s hard to tell how exactly the high orders contribute.
No, it is not. You can calculate via normal linear field theory, how exactly anything contributes. From the field to your ostensibly linear sensor, over an ostensibly rigid sphere, upon which your sensors have been imbedded.
That's just math. Comlicated field math, to be sure, but eminently doable, and deterministic to boot.
One aspect is the interaural coherence that needs to be appropriate. The other main aspect is what I typically term the equalization: Below the aliasing frequency, things are fine anyway.
So why not give us the geometry of your ball-and-mic-array? We don't need any derivative measurement, because given the primary measurement, we can calculate yours on our own.
Above the aliasing frequency, the spectral balance of the binaural signals tends to be more even the higher the orders are that are present. The deviations from the ideal spectral balance also tend to be less strongly dependent on the incidence angle of the sound if higher orders are present.
This is already well-known from the WFS work, of them French and German friends/fiends of ours. That WFS lot. Only they mostly talk about things in rectangular coordinates, whereas us ambisonic fiends do the spherical kind.
Going between those two coordinate systems isn't easy. The transformation spreads any excitation or normal wave *terribly* badly and unintuitively, over the modes of the other representation.
Much of the angle dependent deviations of the spectral balance can be mitigated, for example, by MagLS [...]
What is "MagLS"?
[...] so that the perceptual difference between, say, 7th order and infinite order is small.
That has been done via 3rd order periphonic, with active decoding, already. It certainly needs less channels than straight 7th order pantophonic. So what are you doing here, really?
I can’t tell if it gets any smaller with higher orders. My (informal) feeling is that somewhere between 5th and 10th order is where the perceptual difference to the ground truth saturates, both in terms of equalization and the coherence.
My hearing is that it in fact seems to cohere at about 3rd, or 4th, order, periphonically. That's about 16 independent channels over the whole sphere. Maybe with active, nonlinear, dynanamic matrix processing, as in the case of DirAC.
In the case of 7th order pantophonic processing, the independent channels would have to be 14. So rather close in DSP power. And yet at the same time, they couldn't come close to isotropy, as in the case of 3rd degree ambisonics. They couln't come close to the kind of work needed for full 3D VR work, vis-a-vis, holding a ferry-wheel or roller coaster ride perceptually constant, over the whole ride.
This system would alias, noticeably, unlike full, isotropic ambisonic. -- Sampo Syreeni, aka decoy - de...@iki.fi, http://decoy.iki.fi/front +358-40-3751464, 025E D175 ABE5 027C 9494 EEB0 E090 8BA9 0509 85C2 _______________________________________________ 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.
