I'm pretty sure you're not allowed to bring clocks or timers that make any noise at all. At my LSAT they were telling people they couldn't bring in beeping watches, etc.
However, as luck would have it I took the test on Homecoming day at the U of Montana. Lots of people walking by the windows, talking, yelling, being drunk, and generally making noise. Then to top it all off, in the middle of the second section, the school marching band marched by the window treating us to a nice loud rendition of what I can only imagine is the school's fight song or something. I have to say that's much worse than a couple of beeping watches.