2001 Honda Civic makes a clear beep noise?

2001 Honda Civic EX, two door; I was sitting at a drive-thru window, and suddenly, out of no where's, my car makes a clear beeping noise. Once! My car was in drive, foot laying on the breaks, and my headlights were on. Doors were closed, radio off, and no light lite up saying anything. My SRS light was the only light that was lite, but it has been on since I got it a few years ago. It's bizarre to me because nothing happened, yet I heard this clear beep noise out of no where's. It's been a few days, and I've yet to hear it again, and that was the only time I've heard the noise. Does anyone have a clue as to what it may be? I'm 50% deaf, so you should know its loud when I say it was loud enough. Please let me know your thoughts or if you've experienced this same issue.

It could be your car telling you your brakes are low. In my car when I was braking in December my car would ding and the brake light would come on and go off quickly