Virtual ear muffs created by drinking lots of beer. Music and voices seem muffled and therefore less obnoxious, especially when generated by the person wearing the muffs. They also usually convince the wearer that their singing voice is far better than it actually is.
The neighbor's beer muffs convinced him that the music he was blasting and shrieking along to at 3 in the morning wasn't loud enough to bother anyone.
When you're drunk and find yourself dancing to top 40 songs that you normally hate. Similar to concept of beer goggles
Miley Cyrus sounds a lot better after a couple of drinks, when you have beer muffs