Well on my current iPod which I believe has the old EU cap ( I understand the new one is has been lowered) really isn't load at all when travelling on public transport especially the tube I can barely hear the song or podcast, at 1st I thought it was the headphone so I lashed out £70 on new Bose headphones supposedly they were noise cancelling and best in market, and even that didn't help, albeit they were lot better than iPod headphones.
I had the same problem, when my faulty Australian model iPod Touch was replaced under warranty in the UK. It just found it wasn't loud enough when out in places with a lot of external noise, like walking down a busy street.
You need to change this file, replacing 0.83 with 1.00
/System/Library/PrivateFrameworks/Celestial.framework/RegionalVolumeLimits.plist