The only setting that I see is under User configuration --> User Profile Management and under particular user --> Under Meeting Preferences --> Entry announcement is by default set to Beep + Name. I assume if you set it to Beep only for all users you might accomplish what you are trying to do.

also try the same setting under the User Groups, you may be able to set it for the whole group here.

I haven't tried this, so this is just a hint for you to try..

:JoeL