What we've said up to now with regards to sinusoids is a fundamental truth upon which we will base the rest of our sound reality. An aspect which contributes a lot to the characteristics of sound is its harmonics.
Psychoacoustics studies the brain's sound elaboration mechanisms. A knowledge of such mechanisms is indispensable for the practice of sound engineering, in that it allows, through appropriate manipulation, very sophisticated sound-effects to be obtained.
This effect adds light saturations to the input signal. As already mentioned, a saturation generates new harmonics based on the frequency content of the input signal. Therefore, the exciter effect is capable of generating high frequencies out of signals which lack them, as is sometimes the case with vocals which, though being in tune, don't bite enough.