Ultrasonic wavefronts may be aberrated if the material through which they are propagating has microstructure, such as metals consisting of many grains. This aberration is caused by the grains having different phase velocities for different orientations. The perturbation to the acoustic wavefront affects the accuracy and reliability of measurements and is a fundamental limit to resolution for many materials.We have designed a closed loop system that can detect the acoustic aberrations experienced by surface acoustic waves, and customize the excitation source in real time to correct them. A light from a pulsed laser is delivered to the material via a spatial light modulator (SLM), which allows any pattern of light to be imaged onto the surface. The surface waves excited by this optical source are aberrated by the material microstructure as they propagate towards their intended focus region. This aberration is detected by an acoustic wavefront sensor, and information from this is used to customize, in real time, the SLM pattern, such that the waves will now successfully propagate to their intended focus.As well as describing the adaptive acoustic instrument in detail, results are presented that illustrate the improvement in data that can be achieved when using aberration correction.