I use my own custom content pack which includes ripped sounds from classic FPS games, and the frequency variation on sound effects ingame is actually highly noticeable, distracting, and unnecessary. I think it would be better to remove this variation altogether, because it'll either produce an unnoticeable effect in gun sound effects that people are less familiar with, or it'll make higher-pitched and/or more-familiar effects sound different and peculiar.

If this is a no-go, then at least make the default option for sounds to not have frequency variation.