Is AUTHOR wrong in the post ? POST : Tldr; Am I the asshole for whistling at work in a professional environment?

I work at a well known large hardware store. While I work, I tend to whistle when I am happy. I was in the middle of an aisle whistling when a customer mumbles something to me. I ask him what he said because I didn't hear him and he replies, "Your whistling, it's very annoying. You should stop". At that point I look at him shocked, because no one has ever told me my whistling was a bother to them. Am I the asshole?