Is this such a big deal?

Okay I had ear phones on and I was listening to music. I was at an ATM in a store. I forgot where I was and started farting out load. I couldn't hear it but I felt the vibration! When I realized what I was doing I turned around and there was this women staring at me with a grossed out look. I smiled and said sorry :) then walked away. She watched for a few minutes then went her way. I told my wife what happened thinking she would laugh but she didn't find it as funny as I did so to speak!