Any sound which is played from Google Chrome is very low pitch, doesn't matter which website or source i.e. video from youtube, music from flash games and etc. However if I open same content in other browser i.e. Firefox everything is fine or if I open some mp3 file from my computer via music player everything is fine again. I am using Ubuntu 10.04 if that matters.
Had that issue as well in Linux Mint 15 and it seems the distros share the same Sound Settings gui. Click your volume-icon, select Sound Settings, go to the Applications tab and adjust the volume for Chromium/Chrome.