I've shouted "hello" quite loudly to 4 people this morning (3 street cleaners and one person in the office). No one has acknowledged my greeting.
Perhaps today I am invisible (and the sound equivalent of invisible).

Although I did converse with Laurent as I entered the building this morning. He is French.

So maybe I'm invisible and inaudible (probably the correct equivalent word) to all except the French.

Or maybe French people are just friendlier than English people in the morning.

makes you think