Beyond the most basic principles of auditory scene analysis, the "cocktail party effect" has for years been stimulating a stronger understanding of aural segregation, to describe the effect of several voices dissolving into one.
A. the "cocktail party effect" has for years been stimulating a stronger understanding of aural segregation, to describe - Infinitive is not required as no purpose is intended.
B. the "cocktail party effect" has stimulated a stronger understanding of aural segregation for years, and so describing - Comma+And requires an IC. Also, 02 verbs on both side of and are not parallel. It should be just present participle 'Descibing'
C. the "cocktail party effect", which has stimulated a stronger understanding of aural segregation for years, describes - Correct
D. the "cocktail party effect", which has for years been stimulating a stronger understanding of aural segregation and has described - No verb for 'CPE'. Fragment
E. the "cocktail party effect," having stimulated a stronger understanding of aural segregation for years, to describe - Noun, Present participle/Noun Modifier, Infinitive....hence no verb for 'CPE. Fragment.