A layer of magnetic particles in a resin binder on a carrier is smoothed by effecting relative movement between the carrier and a vibrating ultrasonic horn having a surface in contact with the layer. The carrier can be a web of fully coated magnetic tape or of striped motion picture film; and can be...http://www.google.de/patents/US4044174?utm_source=gb-gplus-sharePatent US4044174 - Ultrasonically smoothing a magnetic layer on a web
