An elementary description of Fletcher Munson or equal loudness curves

For example an instrument or orchestra is playing in the desert. (Disregarding the fact that air absorbers high frequencies).


When one is so far from the music source that the acoustic intensity is very low only the mid frequencies can be heard.


As one comes closer the perceived bandwidth increases.


The closer one comes the more bass and treble perception is increased.


It follows that if one mixes at a  too low acoustic volume the result will be bass heavy at higher volume.


If one mixes at very high monitoring acoustic intensity the result will be bass thin at lower volume.