Using the wave tank with freezer in Hamburg Ship Model Basin (HSVA), we make clear characteristics of regular waves in arbitrary sea-ice condition. In particular, we investigate the attenuation coefficients of waves propagating under the sea-ice, based on the data of wave height measured by ultrasonic-sensor installed above the water surface. Further, we examine whether the attenuation coefficients obey the power low of frequency or not in variously formed ice. As a result, although the wave height exponentially decays with the growth of ice, the attenuation coefficient strongly depends on the frequency. It is shown that wave condition that the attenuation coefficients do not obey the power low of frequency will exist.
