Sound Propagation, Reflection and Phase

[iamsonic]

The phase of a sound wave can not be changed once it has left it's propagation source.
{Sound reflected does not change phase and does not create cancellation.}

The phase of a sound wave can not be changed by changing the angle of the propagation source.
{Sound from a different angle is not a different phase and does not create cancellation.}

Sound propagation is positive and negative pressure pulsations. A positive pulsation reflected is still a positive pulsation. A positive pulsation from a different angle is still a positive pulsation.

The only reason you may have been taught otherwise is because people take the two dimensional graphic representation of a sound wave far too literally. That is not even close to the case when it comes to three dimensional (real world) sound propagation.

[sound is not really the squiggly line.. That is really a bad representation but it's the best we get for now. It does work well for representation of an AC current but even that is not truly correct.. your RCAs don't have inch worms in them either.]

If you do not understand, please find your nearest sound propagation physicist and see if they can help you understand what I mean.
{if they cannot, then refer them to me so I can give them the Frontal Lobotomy they desperately need}

[korey_hofer]

what about when the waves collide and bounce off each other? that causes cancellation

[iamsonic]

Originally Posted by wenn_du_weinst

what about when the waves collide and bounce off each other? that causes cancellation

No it doesn't. In fact quite the opposite is true. When positive pulsations "collide" the resulting pulsation is more powerful than they could amount to if they had propagated from the same angle and direction.

[korey_hofer]

thats when they join I am talking when they don't join and create standing waves and all that good stuff
I'm not trying to argue just figure it out

[madmat]

Actually the phase doesn't change but your position in space will determine if the wave being reflected is in phase with the wave from the point of origin.

http://hyperphysics.phy-astr.gsu.edu...nd/reflec.html

That explains cancellation quite nicely.

[iamsonic]

Originally Posted by wenn_du_weinst

thats when they join I am talking when they don't join and create standing waves and all that good stuff
I'm not trying to argue just figure it out

I understand that you are trying to understand. {not fight}

Even Standing waves do not create cancellation.
Positive pressure pulsations always join but if they are at a multiple of the frequency, you might not be able to audibly pick out the lower frequency, but even then, it's not truly cancellation. It is simply a frequency masking the other frequency.

[iamsonic]

Originally Posted by madmat

Actually the phase doesn't change but your position in space will determine if the wave being reflected is in phase with the wave from the point of origin.

http://hyperphysics.phy-astr.gsu.edu...nd/reflec.html

That explains cancellation quite nicely.

I've referenced his pages many times.
But unless you break the confines of the 2 dimensional depictions it's impossible to understand how sound really works.

[madmat]

Actually I understand it quite well.

[iamsonic]

Originally Posted by madmat

Actually I understand it quite well.

I figured you might if anybody.

If you understand differently, then I'm not so happy but it's all good.

[madmat]

As I understand it, it's got to do with wave lengths and intersections along those lengths. If you're in an intersection where the waves intersect out of phase you get a drop in volume but as waves are all different lenths you can get both positive reinforcement and cancellation in any position.