I dont think its as extreme as the doppler effect. Its just one of those minor things that your brain done. Like for example, if the sound is coming from behind you, your ears roll off the highs. That helps the brain know that the location of the sound is coming from the rear. Same goes for things below you and above you. If the sound is above you, the highs are rolled off while the things below you are kept normal. This makes sense because we normally arnt looking up in the sky but to the ground.
As for sub frequencies (below 100Hz) most of what you are hearing is actually what you are feeling. Thats why it takes big sub woofers with alot of watts to make you think that theres really bass there. Because just listening to the bass it is really dead and dry. I didnt mean that you cant hear those frequencies. While things travel through the air, i believe it is around these frequencies where it begins to boost in level. The longer it is in the air, the more these frequencies boost. But again i could be wrong and exactly where this starts.
And as far as high frequencies go, they are the most important frequencies for localization of sound. Like i said before, the main fundamental for the human hearing is around 1Khz. Frequencies in the 16Khz range are extremely high, and really like definition. Thats why they are used as more of a source of locolization than actual timbre and tone. Try it sometime, roll off everything about 16Khz. Youll notice that the actual timbre, pitch, and tone doesnt really change, but everything will sound a little more out in front. It might not always be the effect your looking for and masterers might involve a little more technique to it besides rolling off, but i notice that about 90% of professionally mastered work is rolled off right at 16Khz. It could be 90% because its the same with the music i like to listen to. There also could be other reasons like we talked about before why they cut off at 16Khz. Like poor filtering conversion up in those frequencies, which could also add to why things tighten up a bit when you cut them off. So that would be an advantage to using a higher sampling rate. But if its being put on CD, then the conversion back to 44.1 will have the same effect in the 16Khz range, and probably worse than y our converters would have done unless you are using a really nice sample converter. Understand what im saying? So basically, its probably best to keep everything at the medium it will be on in the end. Im guessing the same goes for 24 bit recording. If you are using a less than accurate ditherer, you could be doing more damage than good.
Its also ALWAYS good to do a lowcut on the final mix at 30Hz. Nothing below that is good and it will cause alot of mud and low end harmonics.
Anyway, hopefully that cleared things up.
