I was just reading on this last night. I have never done this before but I tried this for the first time last night after reading this site.
http://www.meditationiseasy.com/mCor...hniques/Om.htm
It was actually really calming. I think it's sort of like breathing techniques during labor help you to stay calm. I didn't realize that people actually chanted "aum" like this. I thought that was just something you saw on television.