1. A method of imaging internals of a physical object using acoustic waves, comprising: a) transmitting an acoustic wave field toward the object; b) receiving a resultant acoustic wave field with a receiver, wherein the resultant acoustic wave field is in response to the transmitted acoustic wave field reflected from or transmitted through the object; c) determining a predicted resultant acoustic wave field derived from a model of the object; d) determining a residual between the predicted resultant acoustic wave field and the resultant acoustic wave field; e) back propagating the residual to determine corrections to the model of the object, wherein back propagating the residual comprises either holding the speed parameters constant while updating the attenuation parameters or holding the attenuation parameters constant while updating the speed parameters; f) refining the model with the corrections to the model; and g) iterating steps (a) through (f) to successively refine the model of the object over a number of iterations until a predefined condition is reached.