This one was invented by Leonardo ( like everything else) back a few years ago.
It's the LoudPot.
If you must listen to the radio or some music and don't want to use your earphones, the pot will amplify the sound enough for you to hear it without disturbing Yogi sleeping behind the bushes.
Franco
For the record, Leonardo used Atrac compression on his Sony Walkman.

I always do this with my alarm watch. It makes a barely noticeable difference.

More than amplifying the sound I think that it just reduces the angle , you do need to have it pretty close to your head so there is little chance of annoying someone else.
Mind you it will also depend on the output level of your player.
Franco