Is produced in a free plate of lamb waves in plane strain wave. With the change of incidence and frequency, different in every point of the modal structure is divided into symmetrical (s-type) and asymmetric (type a), due to limited objects between two parallel surfaces and the formation of p-wave and s-wave combination of wave and the upper and lower surfaces of zero stress in plate, spread it over the entire object, for elliptical motion of the particle.