I stumbled on this Classic today (Can opera singers shatter glass with their high notes?) and just wanted to toss in my two cents for an update. On an episode of Mythbusters, the guys brought on vocal coach Jamie Vendera who proceeded to shatter a wine goblet with his unamplified voice. You can see a video here (A Mythbuster’s Glass Shattering Montage), posted by Vendera himself. The break occurs at 2:09 with a slow-motion replay at 2:24.