My Gralab 525 has a four position sliding switch marked "metro-no tone-tone-warn" . If yours has a similar, just slide the switch to the "no tone" position. Unfortunatly, there isn't any way to silence the tone when setting times. Like mine, you are stuck with it. I think its there so you dont accidently bump a button in the dark and change time and not know it. While it may sound loud to you being in the room with it, I dont believe it loud enough to disturb neighbors.
Yah, that's my problem. I have turned off any beeping when the exposure finishes using the slider you mentioned.
My concern is with the sound when setting the time.