Abstract

Media noise has been investigated as a function of both the isothermal remanent magnetisation (IRM) and DC-demagnetisation (DCD) processes on a modified audio transport. Captured noise time series from a given remanent state has been analysed for spectral content using signal processing software. These noise spectra display changes in magnetic microstructure of the tested media with remanent state. Measurements have been made on a range of commercial and laboratory produced tapes. The paper concentrates on examples of commercial samples which have been chosen to indicate various noise characteristics. Conventional media usually show similar features, but changes in remanent state noise has been observed in tapes for new formats and in recent manufacture of conventional formats. This indicates changes in magnetic microstructure associated with new particles and dispersion techniques.