This is one I LOVE! In our house we have the rule that we don't yell at each other (parents included). It's okay to be frustrated but you aren't allowed to yell. If the kids start yelling, I just say, "Watch your tone" and they know it means they better try a different voice.
This is also really helpful when they start to talk back to me. (Why do some parents tolerate this?) I raise my eyebrow which means - you better rethink what you are doing. Then I say -with an edge in my voice - "Watch your tone. I'm your mother." They know they better try again.
How do you handle frustrations in your house?