I made an mp3 player from a scrap of a strobes led bulb. Anyway, the board died and I removed the player and the speaker. I drew a beautiful case in corel and cut it in MDF 3mm. In this case the speaker area is isolated from the player board. I opened 2 ducts to the air outlet generated by the loudspeaker, works well, until I was impressed with how high it plays. If you do not have a led bulb scrap with sound, it also caters for generic Chinese DIY mp3 players.
Hope you can help with your project, feel free to make improvements. Sorry for Neanderthal English.