Newer version of Nautilus no longer offers audio preview on cursor rollover icon. Mint includes Sushi as preview for all kind of files using spacebar. Gloobus-preview offers better support and nicer interface.
Just follow the steps below and you do not even need to restart Nautilus or do anything. Install PPA, Update, install packages, done. That will remove Sushi as well.
sudo add-apt-repository ppa:gloobus-dev/gloobus-preview
sudo apt-get update
sudo apt-get install gloobus-preview gloobus-sushi