I used a combination of a big-mouth Miller Lite bottle stuffed with loose change (with a cap from home that I sneaked in), plus that orange emergency whistle I posted earlier. The bottle was definitely loud -- but not too loud. I was able to shake it every defensive play without pissing people off too much. The whistle was extremely loud and I only blew it on the most important 3rd downs, and even then, only for short spurts. I sit immediately adjacent to the Section 610/611 the tunnel, and at times there were two State Troopers standing in the tunnel while I blew the whistle -- they didn't care, but I was still worried about blowing out my family members' ear drums.
For this weekend, I plan to bring earplugs for my whole family -- that way I can ramp up the whistle blowing without feeling too guilty.