Sonic technique is an acoustic exploration, and analyzes the propagation of the signal inside the material with frequencies up to 20 kHz. The method uses higher wavelengths and less resolution but has the ability to reach greater depths of penetration into the material. In tomography sonic technic is considered, for each signal source station, a discrete number of receiving stations to form a fan of ideal paths of the transmitted signal, differently oriented from the direction of the initial wavefront. For each position of the receiver, the measured parameter reflects the physical-mechanical characteristics of the material crossed during the wave propagation path. Ultrasonic testing uses high frequency (greater than 20,000 Hz) sound waves to characterize the properties of materials or detect their defects. Acoustic waves are generated by transducers, travel through the material, and are received at the surface. Analysis of the signals by the receiving transducer provides information about the media through which the signal has propagated.