Three under is almost always noisier than split finger because folks usually have to raise the nock point quite a bit higher, changing the tiller ever so slightly. Going to a feather rest, which is even higher than the leather or velcro that was probably there initially, exacerbates the problem because it forces you to raise the nock point even more.
Fast flite type strings are also usually noisier, at least higher pitched, than dacron strings. A lot of folks use cat whiskers, but they give off what I consider a buzzy sound as well. I use Wooly Whispers instead. Any residual string noise is more muffled, I think.
Of course, as Karrow has pointed out, a light arrow also contributes to more string noise. Good luck.