Your levels are probably peeking. Check your peak meter and if you don't know what that is look for a meter that when you play your sounds it shows their level in decibels, kind of like what you would see on a stereo with the green yellow and red. It will most likely be in the red which means distortion/clipping. If so, just turn down your sounds or tweak your effects until its in the yellow or green. You should notice a difference pretty quickly. good luck!