I prefer to just use my http://tvbgone.com that I put in a hollowed out old cellphone. Great for those sports bar moments when I just want to stop hearing...
Sports bars certainly aren't my favorite bars, but this just seems rude. It's supposed to be a loud place.
I actually haven't used it - it's just for fun. Full disclosure - I live in Pittsburgh where sports are annoying everywhere: bar, doctor's office, etc. That's what I hate - having everything be covered with TV glow - especially sports fetishism...
Just to add to what carbonica said: nobody is forcing you to go to sports bars, if you don't want to be there then go find a quiet bar, don't come in and turn off what we're watching.
As said above - there are like 2 quite bars - they do mak for good filters though.