First you have to meditate for about 10 minutes, but the longer you meditate the better. Next visualize 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.
(Caution: This will be really loud )
This is a very difficult Sono tech and shouldn't be attempted by beginners. This tech also makes use of aerokinesis.
Start somewhere enclosed where you can be very loud without anyone caring. Compress all the air in the room into a small sphere in front of your mouth. Breathe in this compressed air energy so that there is no air energy around you at all. Blast a scream out. This will use all of the energy you took in.