A landscape of sound.
Imagine that the brain has many areas that react to a certain input. There
is an area that mainly acts on sound, one that mainly acts on colors, one
that mainly acts on how you feel (what
Antonio Damasio calls 'the body state')
The important word here is 'mainly'. Because, there is extensive interconnection between those area's, there is an exchange of information to built your perception. Call it a landscape of neuronal activity, all over your brain, that couples and integrates all those inputs (external and the internal body state) and which leads to a particular state of 'perceiving' the world around you, sound, sights, emotional state, etc. A nice example, related to the total integration of sensory inputs to the perception of audio, is described by Floyd O'Toole, VP of Acoustical Engineering at Harman, in an article called Audio science in the service of Art. The article is quite long to download, but this excerpt makes this particular point.
So, we are unknowingly building, revising, redoing that perception landscape while we go about our business. But the actual vibrations of those hairs in your inner ears are only ONE input of many others. That particular vibration information gets integrated in the total picture. But unavoidably, in that process, much of it is thrown away. The brain uses this, discards that.
Now, if you are trying to listen attentively to a particular sound, the 'gain' of the sound area is turned up and that of the other areas is turned down. You can be so immersed in listening that you hardly know what's going on around you. You can tune the attention of your brain. In fact, that gain can be turned up so high that you think your hear a sound that isn't there. You can create a certain landscape in your brain that is totally imaginary.
Just making it up
Lets taken an example from vision because vision experiences are much easier to discuss. Focus your attention on your mother's face. Got that? OK. Now, I assume your mother is not right there with you (if so, try your father's face). Do you realize what is going on? You 'see' something that isn't there, that is constructed by your brain from memories. A figment of your imagination if there ever was one. Now, very likely you also have a particular emotional feeling, connected to your mother. You may remember a nice meal she cooked, or you remember her serious illness last year, or you feel guilty because you haven't called her lately. All constructs from your brain, created without physical perception inputs.
It's even worse. If indeed you remember that nice meal, you probably 'see' how she smiled at that occasion when you complimented her. Or, if you remember the sickness, you probably 'see' her as a sick person. If it was a serious sickness, chances are that you actually 'feel' bad. Not only does the brain create a perception all by itself, it also selectively 'shapes' that creation depending on which memory you happen to access and it influences your 'body state' to match the perception. When you imagine a bad situation, your body also starts to 'feel bad'.
