Why cant you hear a phone ringing inside a jar?

You can't hear a phone ringing inside a jar because the jar acts as a barrier that contains and dampens sound waves. Sound travels through air by creating vibrations, but when these vibrations hit the solid surface of the jar, much of the sound energy is absorbed or reflected, preventing it from escaping. Additionally, if the jar is sealed, the lack of air movement further diminishes sound transmission, making the ringing nearly inaudible from outside.