DC and modulation noise in magnetic tape

In a perfect particulate recording medium, noise would not be a function of magnetization. In practice, two types of noise occur which are functions of magnetization-dc noise and modulation noise. Both of these usually have been attributed to either nonuniformity of particle dispersion or imperfections in tape motion. The significance of surface effects has been overlooked in the past. A new experimental technique is described, which makes it possible to determine whether a particular type of noise is fixed or random relative to location along the recording medium. It also enables comparison and identification of noise produced in various ways. It has been possible to isolate and measure the components of dc and modulation noise produced by surface asperities and bulk non uniformity. Apparent anomolies in previously observed spectral and amplitude characteristics of dc and modulation noise has been resolved.