In a paper conveying apparatus of an image reading apparatus, image copying apparatus, etc.,  sometimes a jam occurs when the paper moves along the conveyance path.  In general, a paper conveying apparatus is provided with the function of determining whether a jam has occurred by a paper being conveyed to a predetermined position inside the conveyance path within a predetermined time from the start of conveyance of the paper and of stopping the operation of the apparatus when a jam has occurred. 
On the other hand, if a jam occurs, a large sound is generated in the conveyance path, so the paper conveying apparatus can determine whether a jam has occurred based on the sound which is generated on the conveyance path and thereby detect the occurrence of a jam without waiting for the elapse of the predetermined time. 
A paper jam detection apparatus which detects a jam sound, converts it to an electrical signal, amplifies the electrical signal, and detects the jam by the specific frequency component which is included in the amplified electrical signal has been disclosed (see Japanese Laid-Open Patent Publication No.  2001-302021).  By experimenting on various types of jams in advance, sounds which are generated when jams occur are detected, how strong the amplitude is for each frequency component is processed and analyzed, and the frequency component with a large amplitude strength is set as a specific frequency component.