Can a voice get loud enough
and high enough to break glass?

The answer is yes. The idea is that the singing voice would create sound waves that make the sides of the glass bend back and forth so far that the glass cracks.

When you tap the side of an empty drinking glass, it always makes the same sound—though that sound gets louder when you tap harder. This is because the sides of the glass bend back and forth—very slightly and very quickly—at the same speed each time. The speed of this back-and-forth motion is the natural frequency of the glass. A thicker glass will have a slower natural frequency, which creates a deeper sound, than a thin glass.

When the pitch of a singer’s voice matches the natural frequency of the glass, each sound wave gives a little push against the side of the glass that is in perfect time with the natural frequency of the glass. Each push adds a little more bend to the glass, just as a well-timed push helps a friend on a swing go higher. As a result, each movement of the glass becomes bigger and bigger until the glass cannot bend any farther, and it breaks.

But you can listen to an opera without worrying about your goldfish bowl. This works only on very thin glass.