Visualisation of magnetic features on analogue audiotapes is still an important task

摘要

Today, most of the recordings handed in for analysis are digital but there are still cases where analogue tape material has to be investigated. Evidence audio seized from or handed in by private persons has often been recorded in an analogue format, especially on audio cassette recorders or analogue Dictaphones. In cases where an authentication of analogue audio material is required, visualisation of magnetic features is most effective. Visualisation is able to reveal features such as track width and position or shape of head marks. Visualisation adds a dimension to the analysis of audio-tapes that is not present in the oscillogram nor the spectrogram. These show only the phenomena that are within reach of the replay head.