...so just when I got the nerve to make the sign, another coworker saw me laminating it and kinda chuckled.

She commented that "It's good you're laminating it because that would get ripped down..."

That's when I lost my nerve. I'm sure MOUTH ALMIGHTY knows that the sign is directed towards her. There are only three four people in our building and she talks the MOST... and loudly.

While I understand that part of her job responsibilities require her to be on the phone, EVERYONE can hear EVERY part of her conversations (even the boss has closed his door when she gets going)

Sooo... I think addressing everyone would be the most diplomatic thing to do. While it's not my intention to single her out, she will automatically know to whom I'm referring because she talks the most and loudest... GOODNESS...

On an interesting side note. The coworker who stated that LOUDMOUTH would be offended also stated that she's bothered by the noise level as well... go figure