radiation pattern math question

blu_line · 29th October 2002, 05:32 PM

Hello all,

I am moddeling my speaker to be in Software.
Reading material is :
1. Loudspeaker and HeadPhone handbook by Borwick
2. Acoustics by Beranek
3. My old physics book
4. my old Telecom syllaby/text book (transmission lines and antennas)

So far i have been able to program 1 simple and 2 simple point sources and let it produce quite nicely a polar plot.

The problem is the plane piston source.
I do not know how to translate the formula into a nice piece of c-code !

Can any one help ?

For those who have the books
It is about formula 1.18 of [1]
or
formula 4.17 of [2]

best regards,

Simon

f4ier · 29th October 2002, 09:40 PM

I take it you're having problems with the directivity term. The Numerical Recipes Home Page might interest you

Good luck!

Isaac

blu_line · 30th October 2002, 05:14 PM

thanks for the link.

Did not really find what i was looking for (except after paying for the code). But th e direction / hint was more than fine.

I was able to code the formula and except for some minor multiplication factor i got the pictures i was after.

Thanks

grtz

Simon

planet10 · 30th October 2002, 05:21 PM

This little appendix might provide some clues as well.

dave

MJK · 31st October 2002, 04:24 PM

Blu-Line,

If you go to my website, look in the TL Theory Section, open the Calculation Algorithm article, then find Figure 4.6, it shows a series expansion that calculates the acoustic impedance for a piston in an infinite baffle. I think that is what you are looking for, an expansion for the Bessel function to calculate the radiation pattern for a piston in an infinite baffle. You just need to extract the series expansion term and change the equation appropriately.

Hope that helps,

Martin
www.quarter-line.com

blu_line · 31st October 2002, 04:58 PM

Thanks for the link.

I have scanned it quickly (thorough read later), but see you work with the acoustic impedance. Why not pressure ??

(They are related anyway !)

grtz

Simon

MJK · 31st October 2002, 05:04 PM

Hi Simon,

The acoustic impedance is used as a boundary condition for my method. I do calculate the driver's volume velocity and the pressure to get the SPL which is plotted in my results.

Hope that helps,

Martin
www.quarter-wave.com

29th October 2002, 05:32 PM	#1
blu_line diyAudio Member Join Date: Jan 2002 Location: The Netherlands	radiation pattern math question Hello all, I am moddeling my speaker to be in Software. Reading material is : 1. Loudspeaker and HeadPhone handbook by Borwick 2. Acoustics by Beranek 3. My old physics book 4. my old Telecom syllaby/text book (transmission lines and antennas) So far i have been able to program 1 simple and 2 simple point sources and let it produce quite nicely a polar plot. The problem is the plane piston source. I do not know how to translate the formula into a nice piece of c-code ! Can any one help ? For those who have the books It is about formula 1.18 of [1] or formula 4.17 of [2] best regards, Simon

29th October 2002, 09:40 PM	#2
f4ier diyAudio Member Join Date: Sep 2001 Location: Sydney	I take it you're having problems with the directivity term. The Numerical Recipes Home Page might interest you Good luck! Isaac __________________ Crossover/Subwoofer Simulator

30th October 2002, 05:14 PM	#3
blu_line diyAudio Member Join Date: Jan 2002 Location: The Netherlands	good direction thanks for the link. Did not really find what i was looking for (except after paying for the code). But th e direction / hint was more than fine. I was able to code the formula and except for some minor multiplication factor i got the pictures i was after. Thanks grtz Simon

30th October 2002, 05:21 PM	#4
planet10 frugal-phile(tm) diyAudio Moderator Join Date: Oct 2001 Location: Victoria, BC, NA, Sol III Blog Entries: 5	Re: good direction This little appendix might provide some clues as well. dave __________________ community sites t-linespeakers.org, frugal-horn.com, frugal-phile.com ........ commercial site planet10-HiFi p10-hifi forum here at diyA

31st October 2002, 04:58 PM	#6
blu_line diyAudio Member Join Date: Jan 2002 Location: The Netherlands	pressure instead of impedance Thanks for the link. I have scanned it quickly (thorough read later), but see you work with the acoustic impedance. Why not pressure ?? (They are related anyway !) grtz Simon


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31st October 2002, 04:24 PM	#5
MJK Account disabled at member's request Join Date: Feb 2002 Location: Clifton Park, NY	Blu-Line, If you go to my website, look in the TL Theory Section, open the Calculation Algorithm article, then find Figure 4.6, it shows a series expansion that calculates the acoustic impedance for a piston in an infinite baffle. I think that is what you are looking for, an expansion for the Bessel function to calculate the radiation pattern for a piston in an infinite baffle. You just need to extract the series expansion term and change the equation appropriately. Hope that helps, Martin www.quarter-line.com

31st October 2002, 05:04 PM	#7
MJK Account disabled at member's request Join Date: Feb 2002 Location: Clifton Park, NY	Hi Simon, The acoustic impedance is used as a boundary condition for my method. I do calculate the driver's volume velocity and the pressure to get the SPL which is plotted in my results. Hope that helps, Martin www.quarter-wave.com

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