Philip - TextBlade makes about as much keystroke sound as a MacBook Pro laptop, which are resonably quiet for use in meetings.
Premium desktop keyboards like the DasKeyboard make quite a bit more sound, with loud clicks on each stroke.
Some people really love that click sound, which is fine at a desk, but most would not want that much noise when having a meeting.
Since TextBlade is designed to go anywhere, we designed it to be fairly quiet, while still giving a satisfying "thunk".
In fact, TextBlade has special acoustical damping components specifically engineered to damp and refine the sound.
If you really need to rig for silent running, you'd probably fall back to the glass touchscreen, and touch it very lightly. That's the quietest mode of all.
Even with a touchscreen though, it all depends on how vigorously you strike it. You can make a lot of noise on glass with fingernails and hard strikes.