Aspies (and people on the spectrum in general) are known for having low frustration tolerance. An explanation for that can be found in the way Aspies think. Asperger's expert Simon Baron-Cohen explains that Aspies are more systemizing and less empathizing than NTs. Wired has an online version of Dr. Cohen's Autism-Spectrum Quotient quiz you can take - I score in the 30's.
So what does systemizing have to do with irritability? I think the answer can be found in Dr. Daniel Kahneman's work. I have often been asked, "Do you ever stop thinking?" When we systemize, we work in the part of our brain Dr. Kahneman calls system 2. How do you tell if you're in system 2 versus system 1? Kahneman posited an "effort diagnostic." You're definitely in system 2 if interruption by a concurrent activity — say someone practicing trumpet while you're trying to read the paper — proves irritating. Unlike NTs, who basically run on system 1, Aspies are usually running on system 2. As such, the chance of an interruption irritating an Aspie is much higher than NTs.
Although I can't change the way I think (and wouldn't want to if I could), I can reduce the chance of being interrupted. When I'm at home I tend to wait until nobody is around to do work that requires the most focus. Interruptions still can't be completely avoided, so I've trained myself to react with less anger when I get interrupted. My reaction used to be, "Argh! You've made me loose my train of thought!" Now I'll mostly ignore the interruption while holding up a finger to let the person know I'll get to them in a minute. When I complete my thought I'll stop to respond.