Any computer programmers???

felmus · #1 Jul 18, '12, 8:16 am

Is there anyone here who could help me do a simple project?

I used to do programming as a hobby in my teen years, but eventually dropped it due to lack of time. Recently I thought up an interesting programming project that might help me in some of my work, but I don't have the skills anymore to put it together. Someone who routinely does this kind of work should have little difficulty, though.

It has to do with basic acoustics and graphing comb filter effects.

AndrewW94 · #2 Jul 18, '12, 9:28 am

I may be able to help. What specifically do you want. (What does it do, how does it get the data, what languages could be used etc.)
God bless you,
Andrew

Byrnwiga · #3 Jul 18, '12, 9:31 am

I'm also a programmer. I'll reiterate the questions of the previous poster. You'll need to explain in some detail what is needed since I have very little knowledge of acoustics

.

-Byrnwiga

felmus · #4 Jul 18, '12, 10:58 am

Thanks for your responses. Here's the idea.

A single window (I'm in Windows 7, btw) with two areas: top and bottom. The top represents a 2-dimensional Cartesian plane from a side view. The lower edge of it representing the floor. The dimensions of it represent, say, a 14 ft wide by 12 ft high space (or be adjustable). Within this plane there would be two moveable points. One represents a sound source, the other a listener (or microphone). Here is where the acoustics come in.

There are two sounds we want to take into account. The direct sound, which goes straight from the source to the mic, and the nearest reflected sound (the one I am concerned with in this program) which bounces off the floor and hits the mic at a later time. Since this indirect sound takes longer to travel the distance to the mic than the direct sound, it creates a comb filter effect. That is, the frequency response of the sound at the mic is changed due to the combination of the direct and delayed sound.

The bottom area of the program is just the graph of this effect, which changes as the points in the upper area are moved. That's it.

For the most part, the math involved would require figuring:

1. The strength of the direct sound (diminished by the distance between the source and the mic according to the inverse square law).
2. The point of reflection off the floor (depending upon the coordinates of the 2 points).
3. The amount of delay of the reflection.
4. The strength of the reflection (diminished by the greater distance).
5. The comb filter calculation (probably an adaptation of this) for the graph at the bottom.

I've never seen a handy tool for calculating this in this way. I'm not sure what programming language would be best.

Byrnwiga · #5 Jul 18, '12, 11:04 am

The first thing that comes to mind is the need for an object-oriented language; that seems essential. For example, you'll need objects for a sound source and the microphone. Could you draw a mockup of the window?

-Byrnwiga

AndrewW94 · #6 Jul 18, '12, 3:58 pm

Well, an object oriented language is never essential, it is just easier for lots of people to program that way. My thoughts are that the floor will have to be assumed to be flat otherwise this will get really complicated. It should be fairly trivial to make a text based program where you enter the x, y, and z coordinates of the sound source and the microphone, and the other variables and do all the calculations from that, but it sounds like you want to have a graph and moveable 3D objects which I have never worked with before. However, I'd be willing to try to make it.
God bless you,
Andrew

Byrnwiga · #7 Jul 18, '12, 4:51 pm

Well, it's true that the program could be done in something like an assembly language, but for all intents and purposes (and our sanity) an OO language is the way to go.

Do you have any test data that can be used? (i.e. based on a certain size of room with certain coordinates and so forth).

In terms of the floor plan, are you thinking of a 2D representation with the coordinates entered into text fields? or is it an interactive object of sorts (i.e. click and drag)?

-Byrnwiga

felmus · #8 Jul 18, '12, 7:29 pm

I came across the simple language Processing. It resembles C/C++/Java, which I did for many years, and easily does graphics, so I think I have a handle on it. Just programmed the basics of moving the points around and calculating the reflection.

Yes, the floor is assumed to be flat. If I tried to take into account all that ideally should and could be taken into account, it would get much too complicated. This is mostly just to give a clue.

Thanks.

AndrewW94 · #9 Jul 28, '12, 4:34 pm

Sorry I haven't gotten back to you yet. I'll probably try using java, since I have some experience in that and it will run on your computer without problems. Would you mind posting you existing code. I don't know much about accoustics so it would make it much easier for me. From what you said it sounds like the graph at the bottom is all you need? I've never done a graph like this before but my guess is it is done by drawing lines between points on the function.
God bless you,
Andrew