There are many stories about glass and windows that are so uniquely strange that people often cannot believe that they are true.
As strange as it can be to believe, a man did once fall out of a building trying to prove how strong the glass was only for the panel to fall out (but notably not break), and if a window breaks on a plane it does cause rapid decompression similar to the way it is depicted in films.
Probably the absolute strangest fact about glass, however, is the almost-cartoonish idea that a singer could sing so powerfully that it shatters glass, a common generic convention in comedy shows and cartoons and most memorably depicted in an Ella Fitzgerald advert for the cassette tape company Memorex.
However, despite how impossible it may seem, a singer with a powerful enough voice can actually successfully shatter glass, although the reason for this has as much to do with resonant frequencies as it does with outright volume.
All objects have a natural frequency, which is the level of vibrations an object oscillates at normally. You can actually hear this in action if you wet your finger and rub it across the edge of a crystal glass. That ethereal hum is the glass’ natural frequency.
Voices have a natural frequency, and different notes have different frequencies attached to them, which is most easily seen when attempting to use an electronic string instrument tuner that will display the frequency of particular vibrations.
If you can raise the pitch of your voice to match the resonant frequency of the glass and reach a volume louder than 105 decibels, around the volume of a typical rock concert or particularly loud tennis grunts, you can shatter a glass.
This is much easier to achieve with amplification, but some opera singers and particularly powerful vocalists have achieved this as well.
This has only ever been proven to work with wine glasses; windows are typically far more resilient so a shower karaoke session is not going to require window glass repair.