Natural frequencies and damping ratios of doubly clamped and cantilever alviminum pipes filled with high pressure gas (Argon or, Xenon fuel) or high pressure liquid (Water) were measured using shaker and hammer test techniques. The results show that natural frequencies and damping are a little sensitive to the pipe internal pressure. The damping ratios were slightly affected by the pipe filler material. However, the natural frequencies of the pipe filled with water was lower compared to those filled with Argon and Xenon fuel. The damping ratios measured using a shaker were almost two orders of magnitude lower than those measured using hammer tests. This could be due to the extra damping induced to the system from the magnetic field of the shaker.