Well, it's a new build, and I was under the impression that a single beep means some issue, even though I'm not actually aware of any issue, i mean, all appears to be running fine. My previous asus mobo had no beeps on post, I guess I was going by that.
The fact that the manual has three possible conditions for a single beep is a bit misleading, however.
I just looked at that page in your motherboard manual. I have no clue why they list 'no keyboard detected' under one beep. But what you hear means it passed POST.
If a previous board didn't beep at POST, it could mean it didn't have a speaker, the speaker wasn't working, it was plugged in the wrong polarity, or the board wasn't sending the signal to the speaker as it should have.