I sometimes encounter a problem where for some reason, after importing the sound files and saving the map, the sound files end up "blank" and won't play. No idea why it happens, but there's a simple test to find out if that is the problem. Open up your map, open the sound editor, and find the imported file (under the imported section). Play the sound and verify that it plays. Then go to the sound file that you replaced, in this case, navigate to the Muradin folder and play the sounds there. It should play your sound. If either of these steps plays no sound, or plays the original Muradin sound, you sound file didn't save right.
Delete the imported sound files and re-import them. Save, close, and open the map and test it again. Keep repeating until it works.