Sheet conveying device, automatic document feeder, and image forming apparatus

A sheet conveying device comprising:

• a conveyor to convey a sheet in a sheet conveyance direction;
• a sound collector to collect an operating sound generated by a conveyance of the sheet;
• and
• circuitry configured to:
• extract a feature amount of the operating sound collected by the sound collector;
• and
• determine, at different positions in the sheet conveyance direction based on the feature amount, whether an abnormal conveyance of the sheet occurs until the sheet is conveyed to a given position in the sheet conveyance direction,
• wherein
• to extract the feature amount the circuitry is configured to:
• sequentially cut the operating sound in a given time range from a start of the conveyance of the sheet to an arrival of the sheet at the given position, and
• extract the feature amount sequentially from the operating sound cut in the given time range;
• and
• the circuitry is configured to determine whether the abnormal conveyance occurs based on at least one threshold set as a criteria for classifying a distance of conveyance of the sheet as normal conveyance or abnormal conveyance,
• the threshold includes multiple thresholds based on a number of dimensions of plural feature amounts from a start of sound collection to determination of a corresponding abnormal conveyance, and
• false positive and false negative rates for the multiple thresholds are set lower as the number of dimensions of plural feature amounts increases.