Kim and Chan have reported that solid ~(4)He shows a reduction of the rotational moment of inertia below 0.2 K, which suggests an onset of superfluidity. Ultrasound should be sensitive to mass decoupling caused by superfluidity. If a superfluid component exists, the sound velocity of a porous material filled with solid ~(4)He could increase. We have carried out ultrasonic measurements for a porous Vycor glass filled with solid ~(4)He. Since the reported "critical velocity" is very low, we have adopted a continuous wave resonance technique which realizes the oscillating velocity less than 1 X 10~(-7) m/s. The resolution of the sound velocity is 10~(-5) for small oscillating velocities, and is enough to detect the expected mass decoupling. Although the present experimental conditions are rather limited, no signature of supersolid has been observed.
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