You can't just assume you have depression just because of one day of sadness. You have to wait until you get more...factors or "symptoms", if so, you shouldn't diagnose yourself until you can confirm it by a mental health doctor (Not sure what it's called) or therapist.
Not possible. The air is actually able to travel sound throughout itself without any difficulties. I believe, air actually brings sound closer to the people farther away ; It really helps to stretch sound.
