You know we cannot control what you THINK our tone of voice says in YOUR mind. If I am busy/frustrated/annoyed/irritated and say something that doesn't mean I'm feeling those negative feelings toward whomever I am speaking to, more likely I'm frustrated with myself for having to ask for assistance.

Relationships are difficult enough without adding imaginary problems. To avoid this we ask each other something like "that came out harsh, what's the matter?" Usually it's something simple like he's had a bad day or I'm frustrated with what I'm doing. It works very well, I see my kids doing it too. It also opens the path for communication, if the reason is I've had a bad day then we can expand on that.