I have a late-2009 15" MacBook Pro running 10.6.8. Sometimes I use it for white noise when traveling, but last night when I was using it suddenly all the lower tones disappeared and the sound got very tinny. When I play videos or music, it also sounds faint and tinny. When I use headphones, it sounds fine. And when the computer restarts, there is no bong sound, even though it is not muted when I shut it down. The most fundamental questions is whether this is a hardware or software problem. It still plays sound, in stereo, so neither of the speakers has burnt out. Is there a separate woofer that might have gone bad? If it's software, I've tried zapping the PRAM and doing a SMC reset. I've thrown out sound preference files in ~/Library/preferences/audio/ and ~/Library/Preferences/com.apple.systemsound.plist and restarted. I've checked the sound preferences for anything odd, but it all looks the same as ever, and I've tried changing settings in the Audio MIDI setup, to no avail. I was running Audio Hijack at the time (to make the white noise pinker), so I tried removing that, but no effect either. I even tried reinstalling the 10.6.8 combo update, but no effect there either. Any thoughts or suggestions from anyone? It's a real pain, since not only is the white noise now far too hissy, but more importantly the speaker sound is now too faint and tinny to watch videos or listen to anything without headphones. Help!