Determination of defect length in disk coatings by autocorrelation

A technique is described for measuring the weighted defect length in particulate disk coatings by calculating the autocorrelation of the noise spectra. Data from several disks are presented. The noise-derived defect length assists the identification of the dominant noise generators in the disk coating. Examples are given where the noise is dominated by the alumina particles, pinholes (and similar voids), and buffing damage. Noise management is facilitated with this information.