The present invention relates to systems and methods for signal processing of an ultrasound images. More specifically, a preferred embodiment of an ultrasound imaging system includes a transducer array that provides imaging signals at a first frequency, f.sub.1, and at a second frequency, f.sub.2, into a region of interest. A beamforming system processes image data at a third frequency that is a function of the first frequency, f.sub.1, and at the second frequency, f.sub.2. The processing system processes the ultrasound image using the function of the first frequency, f.sub.1, and the second frequency, f.sub.2. The function of the third frequency is a non-linearly-generated, higher-order, mixing term, f.sub.1+f.sub.2.