I remember my first time changing in public too. I was pretty nervous. There were plenty of people in the restroom at the same time and I thought surely everyone would hear.
But it was at a mall, there was no one I knew, and I'd probably never see those people in my life again. So even if they did hear something... and guessed it was diapers... and cared for whatever reason... it still didn't matter
Since then I've changed in public on a few occasions and still never had a problem. Though I still try to avoid it hehe