Originally posted by uzlessExplain what? It's a surface over a speaker. The surface has salt on it, and the different frequencies produce a different pattern. 😕
Can one of you science type guys explain how this is happening?
http://www.youtube.com/watch?v=Pfs4Rd5f_IQ&feature=related
Originally posted by Ice ColdI understand that. Just can't wrap my head around what the sound wave looks like 3 dimensionally. the salt is showing a 2D reprsentation of the soundwave from what I can tell.
Explain what? It's a surface over a speaker. The surface has salt on it, and the different frequencies produce a different pattern. 😕
Originally posted by uzlessA 3D mock up could be made by mapping the sound waves, and then changing the distance between the speaker and the surface. Then repeating it. The sound waves couldn't penetrate several surfaces, that was my first idea.
I understand that. Just can't wrap my head around what the sound wave looks like 3 dimensionally. the salt is showing a 2D reprsentation of the soundwave from what I can tell.
Edit: I am just blindly guessing this stuff too 😞
Originally posted by Ice Coldhmm, I think that would work.
A 3D mock up could be made by mapping the sound waves, and then changing the distance between the speaker and the surface. Then repeating it. The sound waves couldn't penetrate several surfaces, that was my first idea.
Edit: I am just blindly guessing this stuff too 😞
This is a clear and elegant demonstration of fractals, a foundation of chaos theory. This is how the real world "looks" if we could see the accoustical patterns in our living rooms and class rooms and offices. the geometric patterns are subdiving in harmonic patterns as the frequency increases.
disclaimer: i'm an idiot. this was just a wild guess. as i know there are accoustical physicists playing in RHP, someone is going to come along and really explain it. i just stepped in for the moment to roll the ball in the right direction.
Originally posted by uzlessOk. We have some sound waves that are propagating on a finite medium and the equation that describes the sound wave propagation is a differential equation. But since the medium is finite the differential equation isn't enough and the boundary conditions has to be specified. In this case the boundary conditions are that no vibration is allowed on de boundary. But every time you specify boundary condition in a differential equation it makes only that a certain of solutions may exist. In this case only a discrete set of frequencies is permitted. And we what we are seeing is the physical dispaly of those frequencies. They are called normal modes by the way.
Can one of you science type guys explain how this is happening?
http://www.youtube.com/watch?v=Pfs4Rd5f_IQ&feature=related
Edit to better calrify what is going on: Since only a set of discrete frequencies is allowed only some parts of that plate vibrate. So this why we those patterns emerging.
Let's look at the following differential equation:
y''+y=0
Were y=y(x) and '' denotes second derivative to x. A solution to this equation is y(x) =Asin(x) + B cos(x) which can be verified by substitution in the original equation. On the solutions A and B are some constants that depend on the problem in hand.
Now the thing is that this equation has no boundary equations so it has to valid for all space.
But now like on the video provided by youtube let's impose some boundary conditions. Let us say that this wave only propagates from 0 to a and that on the bondaries the function and its first derivative must go to 0.
y(0)=0=Asin(0) + Bcos(0)=B. So this tell us that the firs constant has the value of 0. So our solution is in fact y(x)=Asin(x)
Now for the second boundary condition:
y'(a)=Acos(a)=0. This is equivalent to the fact the argument of the cosine function being a=k*Pi+Pi/2 with k having the values ...,-2,-1,0,1,2,...
This is what we mean when we say that only a discrete set of frequencies is available as a solution to the differential equations with given boundary conditions.
By the way this is why the atom energies and other useful quantities are quantized. They are governed by the Schroedinger equation, which is a differential equation, and boundar conditions must be applied to it so that it describes a possible physical system.
Originally posted by adam warlockYeah, easy for you to say.
Let's look at the following differential equation:
y''+y=0
Were y=y(x) and '' denotes second derivative to x. A solution to this equation is y(x) =Asin(x) + B cos(x) which can be verified by substitution in the original equation. On the solutions A and B are some constants that depend on the problem in hand.
Now the thing is that this equation ...[text shortened]... boundar conditions must be applied to it so that it describes a possible physical system.
GRANNY.