When sound waves move on the boundary surface between two media with different densities, part of the beam is reflected to the transducer. This phenomenon is called reflection. The remainder of the beam continues on into the tissue, but under a different angle. This is called deflection. As sound waves penetrate the tissue, part of the energy is converted into heat. This energy loss is called absorption. Finally, part of the sound waves are lost in scatter. This takes place when sound waves move through inhomogeneous tissue or in a ‘hard’ boundary surface (= large density difference between two media). Part of the sound waves are reflected in random directions, a small part of which towards the transducer. For a summary see figure 10.
Figure 10. Transmission, reflection, deflection, absorption and scattering of sound waves on a boundary surface between two media.