Abstract: A method of measuring a property of a medium using ultrasound, comprising: transmitting one or more ultrasound pulses into the medium from one or more transmitters and receiving at least a first echo signal and a second echo signal from within the medium at one or more receivers, wherein the first and second echo signals correspond to first and second pulse transmission paths within the medium from the one or more sources to the one or more receivers, the second path being different from the first path; and using the characteristics of the first and second echo signals together with an estimate of the property of the medium and a geometrical relationship between the first and second transmission paths to calculate a revised estimate of said property of the medium. By using two different beam paths within the medium, the first and second echoes will have had slightly different interactions with the medium.