In the data centers I've worked in over the decades, those Big Red Buttons would activate a normally-closed contactor in a breaker panel. When pushed, the contactor would open, and turn off all the circults in said breaker panel. Not affected
are lights, convenience outlets, door locks, and other non-data loads. Resetting the contactor to the working position was done after throwing all the breakers to the off position, and then turn on each breaker, one at a time.
The only noise that I have ever heard when the Big Red Button was pushed was the loud BANG as the contactor operated. You hear a similar bang in movies in scenes where lights in a large area are turned on and off.
Nothing like the BANG of a 600-amp 3-phase breaker tripping -- experienced that at University of Illinois Center for Advanced Computation. You immediately look for the person holding a gun.