Funny thing is, the bigger camera (GW) makes a smaller tinny "plink" sound, while the smaller camera (GS645) makes a horrendous "CLACK"... This latter appears to be a deliberate noise-maker connected to the shutter release, and I'd like to hear the rationale for that. Certainly not for a shot-counter. And Fuji expert Frank Marshman told me it cannot be disabled.
I wish I could muffle both cameras, but that GS645 Clack does seem unrelated to the cheap plink sound of the GW690. It makes sense that the GW shutter indexing the total shot counter one more digit could make such a sound, but I'm disappointed in Fuji allowing it to be audible.