I didn't want to say to the students, "if you blurt [blank] times, you will have to do this thing that you don't like" because I didn't want them to stop contributing all together, but I still needed them to be less disruptive.
One of the strategies we tried was having a "Blurt" sheet which would keep track of those student's blurts during class; this was just a sticky note that they kept on the corner of their desk where they would give themselves a check if they blurted. I tried this for a short period of time and found it wasn't exactly yielding the results I wanted.
After a while, I decided that the whole class would have blurt sheets ( a little chart I made up and printed off), but they also had another little sheet to put stickers on. The deal was this: if your blurt sheet was empty for that day, you would get a sticker on the sticker sheet at the end of the day. Once a student got to 10 stickers, they got a reward.
I modified this idea and template from a fellow teacher, Ashlee Unrau, who had used it in her lower elementary grade classroom.
1) The few enthusiastic students didn't feel like they were being picked on if the whole class had to keep track of their blurts too. I was watching everyone; not just a select group of students.
2) I noticed that some of my "quiet" students still had blurt moments too, not just my "enthusiastic blurt" students.
3) The responsibility for their behaviour was put back on the students. They had to work and be aware of their own behaviour, but the stickers were a way for them to keep track of this behaviour and allowed them to set their own goals that they could work towards.
I started off with candy treats as rewards, but if I were to do this again or continue it in a different class, I think that I would change the reward to something a little less sugar-based and more along the lines of things like "extra free time on the computer" or "an extra turn sitting on the yoga balls".
It's not exactly a perfect strategy and I know it might not work for another class, but I'm still always improving my classroom management as I work in different classrooms.