Well the thock is produced by the switches, slider housings, and plate, with the RF being plastic slider housing in a metal plate.  A majority of the sound is just coming up from the face of the plate to your ears, so the case material surrounding and below the plate shouldn't matter *that* much.  I would assume the overall decibel level and pitch will be altered somewhat, but probably imperceptible levels.  Maybe someone with the novatouch case can comment on how it changed the sound.