How would you deal with an irate customer?

Well in my mind customer service is always number one. I would never would take it personally first next I would say something like:

"Im so sorry sir or madam, that you are experiencing this issue, but I will do everything in my power to resolve your issue."

Can you work in loud places?

The answer here is up to you. Most likely a help desk area will be loud and noisy and therefore the interviewer is not asking you this to just be nice but actually finding out if you can handle a noisy area and therefore deal with the noise.