A method of categorizing defects in a media item is described. The method comprises the steps of: receiving an ultrasonic image of the media item, where the ultrasonic image comprises a plurality of points, each point having a thickness value corresponding to a normal value, a thin value, or a thick value; identifying one or more blobs comprising contiguous points each having a thickness value corresponding to a thin value; for each identified blob, comparing a size of the blob with a damage criterion; ignoring the blob if the blob size does not meet the damage criterion; and for each identified blob having a size meeting the damage criterion, categorizing the identified blob using the thickness values and locations.