var audiopopup = null;
function popup(url,width,height) {

   var left = (screen.width - width)/2;
   var top = (screen.height - height)/2;
   var options = 'toolbar=no,menubar=no,scrollbars=no,resizable=no,left='+left+',top='+top;

   audiopopup = window.open(url, 'audiopopup', options+',width='+width+',height='+height);
   audiopopup.focus();

}