On 2021-12-01, Jens Ahrens wrote:
For this type of array, the spatial aliasing frequency f_a is dependent on order N and radius R of the array in the exact same manner like with spherical microphone arrays (SMAs): N = (2 pi f_a / c) R
But it is also dependent on the angle of incidence above the equatorial. In wideband theory, if a plane wave hits a ring of discrete sensors just right, obliquely, from the third dimension, there is hell to pay in aliasing.
And of course there's the near, reactive field to consider, with your sort of hard core sensor. Monopoles on top of a rigid sphere, right? The fields near a hard ball, and their equivalent far fields in free space, under Sommefeld, are highly nontrivial, and they couple lateral to vertical field components. Such near fields can of course be symmetric over the equator, but only as long as the overall acoustic field is symmetric that way, too.
In practice it never is. No source, or ambient reflector, like a room, never is. No source really lies on the equatorial plane. And also, if I'm not thoroughly mistaken, the sampling over the sphere, and the sphere-induced near field, amplify the problems.
0th and 1st order are available for all frequencies. 2nd order approx. above 200 Hz 3rd order approx. above 500 Hz etc.
You mean the cutoff, right? Do you quantify the bands in rise above the equator, too?
I cannot comment on calibration requirements because we did calibrate the array…
Against which precise standard? Over the whole of the sphere of directions?
(Nor did we measure how well it was calibrated out-of-the-box.).
Which you should. :)
I don’t actually think that there are any special requirements.
I think there are. And you know, I think you came to the right place: we might even be able to tell you where you're wrong, where you're right, and help you measure and quantify what your product is really about.
Sursounders really like products of your kind to hit the market. They're just the *thingy*, in our beloved technology. It's just that we like to know what they're about, and how to make them the best they can be. 8)
As before, much of the physical limitations are qualitatively (and also quantitively) similar to SMAs.
Pray tell, what is a SMA? -- Sampo Syreeni, aka decoy - [email protected], http://decoy.iki.fi/front +358-40-3751464, 025E D175 ABE5 027C 9494 EEB0 E090 8BA9 0509 85C2 _______________________________________________ Sursound mailing list [email protected] https://mail.music.vt.edu/mailman/listinfo/sursound - unsubscribe here, edit account or options, view archives and so on.
