A real-time magnetic imaging system enables criminal investigators to “see” signs of tampering in audiotapes—erasing, overdubbing, and other alterations—while listening to the tapes.

The new system, developed by the Department of Commerce’s National Institute of Standards and Technology (NIST), permits faster screening and more accurate audiotape analysis than currently possible. The Federal Bureau of Investigation will evaluate the system for possible routine use in its criminal investigations.

The new system, much faster than the one currently in use, centers around a special audiotape fitted with 64 magnetic sensors that detect any anomalies as it plays alongside the tape in question in a tape deck. Software is then used to create a 400 dots-per-square-inch (dpi) image displaying points in the tape that have been tampered with.

A second-generation audiotape imaging system is under development, which is expected to provide ultrahigh image resolution of 1,600 dpi. That system will use 256 microscale sensors designed by NIST.

For more information, visit www.nist.gov.

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