Magnetic scanner for forensic examination of audiotapes

摘要

Abstract: The use of a new Magnetic Media Imaging Instrument (MMII) as applied to the forensic investigation of audio tapes is reported. The MMII is an instrument that produces a 2D image of the magnetic fields on a segment of tape up to 5 cm long, with a resolution of about 3 microns. The dynamic range exceeds 40 dB. This allows the visualization of important characteristics such as stop marks with much greater detail than is possible with conventional means such as ferrofluids. Results of tests representing typical forensic examinations are presented.!1