The "Ch" sound in that mantra is Hebrew, stemming from the letter ח Chet. It is a prolonged gutteral sound in the throat, which is common in words such as "To life!" or לחיים "Le'Chaim!" (a toast in Hebrew). If this is hard to conceptualize, the following instructional video will teach you. While it is very juvenile, hopefully you will get the point (and get a few laughs as well)!