I'd like to know what are the differences in timbre - or the acoustic properties of a sound - that allow us to differentiate between a sound which is quiet (but close-by) and one which is far away.
For example, you can tell when someone near to you is playing an instrument quietly even without looking to see where they are - they don't sound 'far away'.
Hearing a loud gig or a car stereo playing from the next street doesn't sound like it's quiet - it sounds loud, but far away.
But other times we can't differentiate - I sometimes hear a siren on TV and think it's on the street!
I thought only the amplitude (i.e. volume) of a sound wave diminished with distance - does the shape/frequency alter too? Is this ability just to do with having two ears to locate the source - surely someone who is deaf in one ear can still tell an orchestra is playing a diminuendo and not gradually getting further away?!