Oh, Jan, you don't have to remove the applique pieces! Just go with your first idea and put a slit into the background behind where the noise is coming from and pull out whatever is in there. Afterwards you can slip stitch the slash you made if you choose to. If this were already quilted, it would be a problem, but since it's still just a top, it's no problem at all! Many quilters routinely cut slits underneath each and every applique piece to remove freezer paper pieces (and some don't even slip stitch the slits afterwards). Also, many quilters routinely completely cut out the background fabric from behind each applique piece, only leaving a seam allowance. They do that just to reduce the bulk.