A system and method for efficiently transmitting and receiving focused ultrasound through a medium, such as bone, is provided. The focal region of the focused ultrasound is iteratively updated to provide an improved focus through the medium. This method may be carried out using a transducer assembly that includes two or more transmit arrays each operating at a different frequency. An initial focus is set and updated by delivering focused ultrasound with a lower frequency transmit array. The phase corrections determined in the first iteration are applied to subsequently higher frequency transmit arrays and received signals, and the process repeated until a desired focus or image resolution is achieved.
