As long as there is no grinding or ratcheting sound, I would say that it should be normal. In a quiet environment, I can hear almost all my lenses to make some sort of sound while focusing.
BTW, have you identified whether the sound is made by the IS or the AF module?
Thanks for the response, all.
I can differentiate between the IS and AF. The IS is just a teeny weeny sound of a lens shifting inside (sounds normal). It's when the lens is trying to focus that I can really hear the sound like the internal thread turning when focusing. Maybe I'm just too used with the L's. This is my first non-L EF lens aside from the noisy 50mm 1.8 II. But I think even the EF-S 17-55mm 2.8 I had before was quieter than this.
No grinding sound or clicking on the 35.
I will bring this back to the shop to see what the dealer says, I'd also try out their 28mm IS to see if they are the same, since they seem to share the same materials.