The system controls the frequency of an ultrasonic signal to be applied to a waveguide, such that the frequency corresponds to a preferred resonance mode of the waveguide and not to adjacent undesirable resonance modes. The system operates by carrying out a first scan of a predetermined portion of the...http://www.google.com.au/patents/US7353708?utm_source=gb-gplus-sharePatent US7353708 - Ultrasonic generator system
