Hi, Searching through the forums, I have found that many people have problems with the headphone jack on the Macbook Pro. My problem is that, when playing audio through the headphone jack, a weird "whoomphing" or wavering noise is present. It sounds as though the audio is quickly moving from one ear cup to the other. I have made a quasi solution by using audio hijack pro to force mono sound throughout my system, and this seems to have temporarily solved the problem, but I would really prefer to listen to my music and other media in stereo sound if at all possible. I have tried several pairs of headphones, and they all experience the same issue. When I use the headphones on other systems, they are fine, so I don't believe that they are the source of the problem. When playing audio from the Macbook's built in speakers, the sound is normal. I purchased my Macbook in the summer of 2009. The model identifier is MacbookPro5,4. I am running Mac OSX 10.6.6, and I just did a software update check and everything appears to be up to date. Any help would be greatly appreciated. Thanks in advance!