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Xsim-3D development... I could use some math help
Xsim-3D development... I could use some math help
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Old 23rd January 2018, 10:18 PM   #11
bwaslo is offline bwaslo  United States
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Xsim-3D development... I could use some math help
Is there such a thing as a spline curve-fit for an array of complex values??
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Old 23rd January 2018, 10:25 PM   #12
DPH is offline DPH  United States
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Sinc interpolation?
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Old 23rd January 2018, 10:28 PM   #13
bwaslo is offline bwaslo  United States
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Xsim-3D development... I could use some math help
Thinking out loud, here.... Maybe do some sort of weighted average (weight by cosines of the H and V angles?) of Mag/angle formatted values, with the angles first unwrapped?

4D stuff (x,y,z and time/frequency) gets nasty to deal with pretty quickly!
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Old 23rd January 2018, 10:31 PM   #14
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Xsim-3D development... I could use some math help
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Sinc interpolation?
Can you explain? I know of Sinc interpolation for connecting sample points without adding new HF data, but is there such a thing for complex values?
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Old 23rd January 2018, 10:41 PM   #15
bolserst is offline bolserst  United States
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Quote:
Originally Posted by bwaslo View Post
...Otherwise, all my clever off-axis and boundary reflection simulations won't work with anything other than radiating round pistons...
You could expand to include ribbons and ESLs without too much effort, using rectangular piston directivity.
I have found the attached formula to match well with measurements and brute force distributed point summation calculations.
With vertical angle set to 0, the horizontal directivity is that of a line source(ie sinc function) with line length = piston width, similar in the vertical direction using line length=piston height. This formula may provide some ideas of how to approach combining disparate H & V directivities. I'm still cogitating on it...

BTW, the rectangular piston formula in Beranek Acoustics is just the product of the horizontal and vertical line source directivities and does not match as well.
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Old 23rd January 2018, 10:59 PM   #16
bwaslo is offline bwaslo  United States
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Originally Posted by bolserst View Post
I have found the attached formula to match well with measurements and brute force distributed point summation calculations.
With vertical angle set to 0, the horizontal directivity is that of a line source(ie sinc function) with line length = piston width, similar in the vertical direction using line length=piston height. This formula may provide some ideas of how to approach combining disparate H & V directivities. I'm still cogitating on it...

BTW, the rectangular piston formula in Beranek Acoustics is just the product of the horizontal and vertical line source directivities and does not match as well.
Isn't the attached equation the same thing? (product of the horizontal and vertical line source directivities). I don't have the Beranek reference you mention..
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Old 23rd January 2018, 11:08 PM   #17
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The attached Beranek equation uses horizontal width(d1) and horizontal angle(theta1) to calculate the horizontal line directivity, d2 and theta2 for vertical line directivity and then multiplies them together.

The previous equation uses angle theta as angle relative to the piston normal, and phi as projected angle relative to the x-axis.(ie if vertical angle = 0 and then phi = 0deg, if horizontal angle = 0 then phi = 90deg)
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Last edited by bolserst; 23rd January 2018 at 11:10 PM.
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Old 23rd January 2018, 11:13 PM   #18
bwaslo is offline bwaslo  United States
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Xsim-3D development... I could use some math help
bolserst -- thanks. Got it (I think).
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Old 23rd January 2018, 11:15 PM   #19
bwaslo is offline bwaslo  United States
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Xsim-3D development... I could use some math help
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Thinking out loud, here.... Maybe do some sort of weighted average (weight by cosines of the H and V angles?) of Mag/angle formatted values, with the angles first unwrapped?
I meant the angles of the complex result (arrayed by frequency) being "phase unwrapped". To avoid the issue of periodicity of phase values. I'll play with that a bit, see if there's any hope for that.
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Old 24th January 2018, 12:59 AM   #20
bwaslo is offline bwaslo  United States
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Xsim-3D development... I could use some math help
Another thought -- maybe to interpolate on group delay (with polarity) for the phase component? Or phase delay (from unwrapped frequency starting at 0 or 180degree at LF)?
I'll have to hack into the code and do somethings in different order to even try such things -- I currently do each frequency separately and combine, but to get these, I'd have to go through all frequencies per driver (and per reflection!) first do then get delay or unwrapped phase. Messy, but I don't want to give up, at least not yet.
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