First you have to meditate for about 10 minutes, but the longer you meditate the better. Next visualuze air molecules, which carry human speech, all around you. I usually visualize it as the static on the TV when you change it to a channel it does not carry. Anyway visualize it all around you, now feel it, don't just see it. Now here is the fun part. Gather the air molecules into a ball in your hand, pick your target, and blast away. Don't blast towards glass; it has the same effect as a high-pitched sound.