I'm assuming you have Windows Vista 64-bit? That's usually the case with this particular problem.
First off, close your Graal client if it's currently open before doing this. Open your Graal folder on your computer. Once opened search for your 'game_config' file, it will be a text document. Open it, and Find the line, 'tryloadsoundson64bit=false' and change false to true. Save the file, and see if you hear sounds on graal now.
There is a possibility that you will not hear sounds, because Graal is not friendly with Vista apparently, not yet atleast. If you need further help, post reply here and i'll try and help you, or you can use the
Search Option. Also, please post further problems you have in the Tech Support forum which should be 4 sections below this one.