Pass Blob through ajax to generate a file

Try uploading the file as form data

audioRecorder.exportWAV(function(blob) {

      var url = (window.URL || window.webkitURL).createObjectURL(blob);
      console.log(url);

      var filename = <?php echo $filename;?>;
      var data = new FormData();
      data.append('file', blob);

      $.ajax({
        url :  "lib/vocal_render.php",
        type: 'POST',
        data: data,
        contentType: false,
        processData: false,
        success: function(data) {
          alert("boa!");
        },    
        error: function() {
          alert("not so boa!");
        }
      });
}); 

.

<?php 

if(isset($_FILES['file']) and !$_FILES['file']['error']){
    $fname = "11" . ".wav";

    move_uploaded_file($_FILES['file']['tmp_name'], "../ext/wav/testes/" . $fname);
}
?>