Yes, of course. If You want to join 2 files their formats should be identical. For Example, You can join “CCITT u-Law 8-bit mono” with “CCITT u-Law 8-bit mono”. Thus if You have “CCITT u-Law 16 bit mono” You have to convert it to “CCITT u-Law 8-bit mono” (use AudioCompressionManager. Convert method).