Could they hear his headphones

I wondered the same thing too when he and Sean William Scott were standing on the train platform. The way "Doug" looked at "Richard" it seemed like he could hear what he was listening to...which I thought was pretty funny.

"...we in the killin' Nazi business. And cousin, business is a-boomin'." -Lt. Aldo Raine

Goddammit, of course they could hear.

I think so.

It's part of why this movie didn't work. You can't always tell when something's even a joke. For instance I couldn't hear a thing the banjo neighbours' said. I had the impression it was probably funny - but I couldn't hear it.