We obtained the tube voltage dependence of the Wiener spectra of the radiographic mottles of the front and back emulsions made using a low-speed screen and an anticrossover film. The Wiener spectral values of the front emulsion are almost constant, while those of the back emulsion increase with the tube voltage. The spectral values of the front emulsion are greater than those of the back emulsion at most of densities. In order to investigate the reason of these phenomena, we separated the radiographic mottle into the three factors. As a result, we have found that the reason of the dependence of the radiographic mottle is that the contribution of the quantum mottle is less than that of the structure mottle. The Wiener spectral values of the structure mottle of the front screen are greater than those of the back screen for most of the tube voltages. The Wiener spectral values of the front screen decrease and those of the back screen increase with the tube voltage, and the two curves cross at high voltage. These reasons were explained from the spatial fluctuation of the thickness of the screen due to the nonuniform screen structure and the attenuation curve of the x-ray intensity. The tube voltage dependence of the quantum mottle was explained from that of the number of photons absorbed in the screen.