Structural intensity technique is usually used to estimate vibration power flow in structures. This method is used to determine vibration power flow in thin naturally orthotropic plates. Bending wave is considered to find general vibration power transmission in the frequency domain that is not approximated by far field conditions. This intensity formulation defines power flow per unit width of the plates (W/m) similar to that of the conventional idea. Power flow estimation is formulated using cross-spectra of field signals, facilitating the use of FFT analyzer.