Why when people sleeping they will sound 'Zzzzzz'???

Question

Why when people sleeping they will sound 'Zzzzzz'??? we always see in the speech bubbles in carton or drawing..even when we are text chatting in internet, we will use the letter 'z' to tell that we are sleeping?i was wondering this since i was 4 year old...can u plz state ur answer and relevant explanations and reliable sources?

Answer 1

It's supposed to represent the sound of snoring, although that's not really how it sounds.