A method for preventing damage to a document by a document transport apparatus provides a member for receiving the document as a stack of sheets to be serial fed to a feeding station. At least two spaced-apart microphones are disposed at the feeding station and responsive to audio to produce signals representing audio energy received by each microphone respectively. The energy received from each microphone is compared to determine if it is ambient noise or if it indicates that two attached sheets are being fed or a single sheet is being damaged. The document transport apparatus is shut off to prevent damage to documents when it has been determined that two attached sheets are being fed or that a single sheet is being damaged.