At this building I go to, I am always hearing a brief elevator emergency bell ring. I had never thought about it. We have the same elevators at my job, and I never hear it there. One day, I decided to give the matter a little thought, and I figured it out. What are the differences between the elevators at work, and these ones?

1. The doors close a lot more slowly on these ones. The ones at work close as soon as someone presses a floor button.
2. The people only come here once a week, so they are not as familiar with the elevators as they would be at my office.

Now, couple that knowledge with the following (bad, I know, but I used my phone camera, which stinks) picture:

Can you figure out why I keep hearing the elevator alarm bell ring?