Hi inej,
Living on a main through road, we get sirens all the time - living with so many retirement/elderly folks homes nearby the ambulances are up and down all day - so we've given up looking out the window!
Most conversations I can't help but hear on public transport is annoyingly one way - mobile bl00dy phones!!
Must admit to being interested if someone is shouting at another, or squabbling over something - try to make out I'm not, by looking 'past' them, just in case they shout at me for being nosy!