Interfacing with Computer Speakers?

Hello, I have a bunch of old computer speakers lying around, and I would like yo use my Arduino to play sound out of them. Googling around did not provide me with any answers. Can someone point me in the right direction?

One of the speakers lying around has a power cord, so it looks like I am set. Can I just cut off the jack and then send stuff down the wire, or is there something else I need to consider?

Alright, I cut the jack off the end and I am left with two wires. Touching either of them seems to produce a sound, albeit one more than the other. I have a question:

After removing some of the black outer casing, there is a smaller colored (one pink, the other white, the pink one produces more “humming” when touched) wire inside each of my two wires. There is also some “loose” copper wiring that is in the black wiring, but not contained in the colored wires. It makes no sound when touched. What is its purpose?

Thank you for your help.

I have two final questions:

1) I was experimenting with the GND wires before I saw your reply. When I played with them, the volume of the speaker would change. What causes this change and what would the best way to maintain a maximum volume be?

2) What is the best way to keep the GND wires together? Even with plenty of twisting, they come undone fairly often.

I do not want to confuse the matter but that "shield wire" could also be a ripcord in that case that wire has no electrical function, it is just there to help remove outer shielding more easily.

a photo of the cord would be handy..