Perhaps the map is getting hugged to death right now? I can't get any data to load beyond the base geo layer.
EDIT: hmmm, seems to be a bug. I see in the console it's expecting JSON from this url: https://maps.bts.dot.gov/services/rest/services/Noise/CONUS_...
Here's the link if you want to skip the article:
https://maps.bts.dot.gov/arcgis/apps/webappviewer/index.html...