Abstract: A method for evaluating stacking or sorting integrity at an output device of a high-speed apparatus that processes media includes: acquiring an audio data substantially in real-time from the output device of the high-speed apparatus while the high-speed apparatus is in operation, by use of an audio sensor located at the output device; transforming by a processor, the audio data to into a stacking or sorting integrity value; and if the stacking or sorting integrity value exceeds a predetermined threshold, stopping by the processor a document transport of the high-speed apparatus. An apparatus for evaluating stacking or sorting integrity at an output device, and a system for evaluating stacking or sorting integrity at an output device of a high-speed apparatus are also described.