Combined ultrasonic-based multifeed detection method and sound-based damage detection method

1. A method for feeding sheets comprising:

urging a sheet through a sheet transport path;

directing ultrasonic energy toward the sheet and toward only one audio receiver;

processing audio data detected by the audio receiver, the audio data detected during the step of urging, by filtering the audio data into a first frequency band and a second frequency band, wherein the first frequency band corresponds to a multifeed and the second frequency band corresponds to the misfeed;

determining a misfeed in the audio data; and

terminating feeding sheets in response to the step of determining.

2. The method of claim 1 , further comprising processing audio data in the second frequency band to determine the misfeed.

3. The method of claim 2 , further comprising filtering out audio data in the first frequency band prior to said processing the audio data in the second frequency band to determine the misfeed.

4. The method of claim 2 , further comprising calculating an energy of the audio data in the second frequency band.

5. The method of claim 4 , further comprising mounting the audio receiver proximate the transport path using a noise isolating compliant material.

6. The method of claim 1 , further comprising placing the audio receiver proximate the transport path during said step of urging.

7. A method of determining a misfeed in an article processing apparatus, comprising:

placing only one microphone in the article processing apparatus;

placing an ultrasonic energy source in the article processing apparatus;

feeding an article into the article processing apparatus;

generating and collecting data frames of sound detected by the microphone;

processing the collected data frames to determine the misfeed; and

reducing a probability of a false misfeed determination including:

accumulating a number of data frames collected; and

reducing a sensitivity setting if the number of data frames collected exceeds a preselected amount.

8. The method of claim 7 , further comprising calculating an energy level of the data frames and comparing the calculated energy level for each data frame to a jam threshold corresponding to each data frame, the jam threshold for each data frame determined according to the sensitivity setting.

9. The method of claim 8 , further comprising opening a jam count window upon determining that the calculated energy level of a current data frame exceeds its jam threshold, the jam count window for accumulating a jam count, the jam count for counting a number of data frames that exceed their corresponding jam threshold.

10. The method of claim 9 , further comprising issuing a jam signal if the jam count reaches a preselected jam count limit while the jam count window is open.

11. The method of claim 10 , further comprising counting a total number of frames that have been processed and closing the jam count window if the total number of frames that have been processed exceeds a jam count window size.

12. The method of claim 9 , further comprising:

counting a total number of frames that have been processed and closing the jam count window if the total number of frames that have been processed exceeds a jam count window size, including resetting the jam count to zero upon closing the jam count window; and

issuing a jam signal if the jam count reaches a preselected jam count limit while the jam count window is open.

13. The method of claim 7 , further comprising filtering the data frames to distinguish intermittent amplitude peaks and continuous high amplitude data.

14. The method of claim 7 , further comprising filtering the data frames using preselected upper and lower cutoff frequencies.

15. The method of claim 7 , further comprising bypassing a plurality of initially collected data frames.

16. The method of claim 15 , wherein the step of bypassing includes overwriting the data in the initially collected data frames with zero values.