Signal and noise levels in magnetic tape recording

The primary object of the work described here was to determine what properties of the tape and associated magnetic elements are responsible for the noise and signal output levels of magnetic recordings and, if possible, to display in specific equations the pertinent relation-ships connecting noise and signal levels with the physical properties of the tape and polepieces. In the course of the study, methods appeared for decreasing the noise and increasing the useful signal reproduced from magnetic tape. These methods and some of the use that Bell Telephone Laboratories and Western Electric have made of them are mentioned in the discussion. While some of the work described in this paper has implications for more than one type of magnetic recording process, perpendicular recording on tape¹ is the actual subject matter dealt with. In every case discussed, the record medium was 0.050 inch wide and 0.0022 inch thick. Except where otherwise noted, a chrome-steel tape was used at a speed of 16 inches per second.