People turn the car radio down when they start looking for a house number. Nobody hears a house number. The radio is not standing between the eyes and anything they need, and most people, asked why they did it, will laugh and admit they have no idea, and then do it again two streets later. I don’t think it is about hearing at all. Looking for something you have never seen is a kind of listening with the whole of you, and the radio is the one part of the noise you are allowed to switch off. It may be the only moment in an ordinary day when someone quietly concedes that they have a fixed amount of attention, and chooses where to spend it.