If you've ever used a microphone, you probably have some idea of what you sound like, but that doesn't mean there aren't occasions where you're without recording equipment and want to know. If you want to hear how you sound when giving a speech, or how your singing voice sounds, you can find out by using two folders.
As vocal coach Chris Beatty demonstrates in the video above, if you just stick two folders behind your ears it will help you hear how you sound to every else. (You can use your hands if you don't have big items like folders, but that won't work as well.) This is because you're deflecting the deflecting the sound from its origin (your mouth) and hearing more of how it reverberates in the room. While others will hear you a bit more clearly than you'll hear yourself with this technique, you'll get a much better idea of how your voice actually sounds to the rest of the world. How you'll look is another story entirely.