Closed trettberg closed 8 years ago
I think this corresponds to #54, where we discussed a line source for the case of 3D NFC-HOA and we should maybe solve this in the same way?
For the NFC-HOA case we have two possible solutions at the moment:
1) use a normal xs
vector with a length of 3. Ignore the z
-entry of that vector (or do a projection onto the xy
-plane) and always place the line source perpendicular to the xy
-plane.
2) use a xs
vector as in the case of a focused source, which has a length of 6 and contains the direction of the line source beside its position.
I think solution 2 would be preferrable, but I haven't checked how easy the implementation will be. For NFC-HOA, @narahahn stated: " I think the driving functions can be obtained by applying a rotational operation on the sphere."
I also noticed this problem (in 3D WFS) while preparing the AES paper. Since I was considering only vertically aligned line sources, I just replaced xs(3)
with x0(3)
for each driving function so that the propagation distance (and delay) is computed correctly.
For NFC-HOA, we could rotate the coordinate system in such a way that the line source is aligned parallel to the z-axis (as @fietew mentioned). Then we can obtain the driving function in a simpler way. In WFS, however, rotating the coordinate system would be not necessary, and the WFS driving functions can be directly computed as Till proposed.
The NFC-HOA case (#54) was the very reason to look into this.
Maybe we continue the discussion over there. (I think agreement about xs
is the hardest part of fixing the WFS case.)
Yes, I agree this will be solved at #54.
The current formulation of the line source driving function is used for 2D and 3D WFS, but it only works in 2D. To make it work, I think
x0 - xs
should be replaced with a vector perpendicular to the line source, that isx0 - xs - <x0-xs,v> v
wherexs
is a point on the line andv
a unit vector along the line.