Observation

I live somewhat near Galludet University, which is a college for hearing impaired students. The main gate and driveway of the school is located on Florida Ave, a busy street in DC. There is a "push to cross" button at that intersection that triggers in the walk signal. When the button is pressed and the walk signal lights up, it is accompanied by a loud "beeping" noise that lets you know when the walk signal is green. That is the only intersection in the entire Washington area I have found that has a sign AND tone to let you know it is safe to walk.

Let me repeat that. The only audible walk signal I have ever heard in DC in located in front of a school for the deaf.

Do you think someone in City Hall did that as a joke? Seriously. Do you think some dude in Public Works was like "Hey, Bob, we got dis one audible cross walk signal in with da rest of the regular signs, whataya want me to do wit it?", and Bob is like "Hey, trow it up in front a tha deaf school!"