Test another speaker to see if that give you sound. Work from there.
I have never personally experienced a broken Gameboy Speaker.

I picked up a DMG for a reasonable price recently, conscious of the fact that there were a few dead columns and that there was "no sound."  After opening it up and fixing the dead columns, I plugged in a set of headphones to see whether I could get any audio.  Sure enough, the audio worked fine through the headphone jack.  Should I assume then that the speaker is faulty or possibly just has a weak connection?  I am open to swapping it out for another if need be, but it would be cool to know how to fix it also.

I currently have no way of taking pictures.  That being said, given what I've described so far, does anyone have any input?  Am I on the right track?  Is this a relatively practical repair to perform?