Modelling the reflection in TL bends

[Onur]

Hi,

http://www.yildiz.edu.tr/~ilkorur/bend3d.mpeg

The link above is directed to a FEM simulation on my web page. I am a Ph.D. student and I am working on the mathematical model of TL enclosures. Unlike M.J. King model, I am working on a TL which has sudden area changes and acoustical filters, just to be able to use less damping material and improve the sensitivity performance.

http://www.diy-systems.com/en-us/dept_10.html

The link above shows in a way that it can be possible. But in order to perform optimization and fine tuning a math model is what I need !

After dealing too much with neural network approach and electro-acoustical modelling, the time has come to the hardest part. I have to build the mathematical model of the line with bends and all the other perturbations. Performing search over the scientefic databases yield some results but I have to reach to the core in order to understand the basics of modelling. Specially I need to model the reflected waves as given in the simulation above. As I have written in my messages in other subjects, if this subject is considered in complex terms the real part symbolises the energy transmitted through the elbow or terminus and the imaginery part symbolises the reflected one.

I will be glad to receive any leads, links, information, comment on how to model such a behaivour.

Thanks in advance.

Regards
Onur

[GM]

Well, I was going to send you a private message, but since you don't allow them, good luck with your quest.......

GM

[Onur]

Originally posted by Onur
I have to build the mathematical model of the line with bends and all the other perturbations. Performing search over the scientefic databases yield some results but I have to reach to the core in order to understand the basics of modelling. Specially I need to model the reflected waves as given in the simulation above. As I have written in my messages in other subjects, if this subject is considered in complex terms the real part symbolises the energy transmitted through the elbow or terminus and the imaginery part symbolises the reflected one.

I guess there is no one who dives into deep sea of maths when it comes to simulating what is going on inside the enclosure and its' close surrounding. I have conclued this from the number of emails that I have received due to my help request above, which is none.

Anyway, you haven't contribute but you can benefit from the result.

http://www.yildiz.edu.tr/~ilkorur/

There is your simulation. Solves the hyperbolic wave equation on an Unbounded Domain so that you can simulate your favorite geometry and calculate the transmission loss. What this will bring to your work? Optimized absorber placement, standing wave analysis, finding the radiation pattern, oprimization of horn heometry, optimization of speaker placement in TL and other enclosures and so on. No, you don't need MatLab, and you don't need another >1K software, otoh you may benefit from Excel or a similar software for processing the output data.

/Onur

[MJK]

I guess there is no one who dives into deep sea of maths when it comes to simulating what is going on inside the enclosure and its' close surrounding. I have conclued this from the number of emails that I have received due to my help request above, which is none.

You might be surprised, just because you did not receive any response does not mean that others are not working in this area.

[Onur]

Originally posted by MJK
You might be surprised, just because you did not receive any response does not mean that others are not working in this area.

You have been of great help to me. But, this is just funny, if people do work on similar subjects, why they do not help eachother like you do? What is the meaning of bringing up a DIY community anyway, to satisfy the Ego within?

No one has ever mailed to me and shared anything about NRBC, absorbing boundary conditions, non reflecting boundary conditions, Perfectly Matched Layers for Maxwells' Equations or their applications to Hyperbolic Wave Equations. But, instead I did receive mails about how they have solved the problem using MatLab, and how brilliant their solution was (nothing in terms of maths). I have received many advice, to leave the code aside since MatLab was doing more then enough and there was no need for such a code. I think I do have the right to complain against these "ego shows", although I am fully aware that this is my PhD thesis and I have to deal with it myself.

Anyway, if you are talking in the name of other people who has interest in this and didn't prefer to help me with this code, then it is ok, nothing to say there, but if you are talking about yourself, please be confident that my words weren't aiming at your direction, since I will always be thankful for what you have done.

/Onur

[soongsc]

I think most DIYers are not so mathematically involved. Some people have different goals that may not cross with what you are doing. Lonely path sometimes. About 80~90% of engineering solutions up to know, I had to figure out myself from whatever information I can find.

While your simulation looks cool. I think the way waves interact and change after the interaction effects what we hear. One partucular area is driver cone shape and configuration. Ever since I listened to drivers with phase plugs and without, I am convinced that the shape of the phase plug would benefit much more from FEM analysis than the transmission line, especially at the high frequencies. Of course the transmission line is very important also, but unless complicated acoustic filtering is desired, FEM modeling may not yield much differences from a larger scale analysis.

[MJK]

But, this is just funny, if people do work on similar subjects, why they do not help eachother like you do? What is the meaning of bringing up a DIY community anyway, to satisfy the Ego within?

I am sure each person has his/her own reasons for sharing or not sharing, personally I have stopped making everything I do available once I found some people were using what I was giving away to make money. But as you point out this is DIY, so that is what I do. I try and write all of my own software for every problem I want to study. That is half the fun and how you can learn a lot. I am not concerned with what other people claim they are doing or any ego issues. I don't feel anybody owes me anything and I don't feel I owe anybody else anything. Sometimes I respond to posts on the forums and sometimes I just don't have time. I do try and answer all e-mails I receive.

No one has ever mailed to me and shared anything about NRBC, absorbing boundary conditions, non reflecting boundary conditions, Perfectly Matched Layers for Maxwells' Equations or their applications to Hyperbolic Wave Equations.

Can't really provide any comments on those topics because I have no idea what they are, obviously way beyond my limited understanding.

I think I do have the right to complain against these "ego shows", although I am fully aware that this is my PhD thesis and I have to deal with it myself.

I don't think you have a right to complain, I am not sure why you would even care about these types of responses. Ignore or delete them. If you present your work in a public forum you are inviting comment and should expect feedback. Some of the feedback will probably not be positive. Get over it and take the positive and constructive comments and work with them. The worst thing is when nobody responds and you are completely ignored. That is worse then negative feedback, I speak from experience.

Anyway, if you are talking in the name of other people who has interest in this and didn't prefer to help me with this code, then it is ok, nothing to say there, but if you are talking about yourself, please be confident that my words weren't aiming at your direction, since I will always be thankful for what you have done.

There are all kinds of people working on the same things you are in their own way, including myself. Personally I have stayed away from group efforts because I like to be independent and not have to depend on other peoples efforts or have my efforts be on somebody elses critical path. I work to my own schedule on my own interests. My focus shifts as I move along and encounter topics of interest. I think there are a lot of people in the same situation. I already have a boss at work and one at home, my hobby is my own. For most, this is a hobby that probably only gets the little time left over at the end of the day. If I were you, I would try to be totally independent and do everything myself. Isn't that part of the process of studying to get a Phd?