PURPOSE: To facilitate the insertion of pipes or bars and surely prevent a fluid pipe from generating vibration and noise by positioning the flexible pipes or bars of a specified dynamic friction coefficient in the space between a sheathed pipe and the fluid pipe piped in the sheathed pipe made to abut on the sheathed pipe and fluid pipe.

CONSTITUTION: A flexible fluid pipe 2, in which fluid such as oil, water, etc., flows, is piped in a flexible sheathed pipe 1 forming a double pipe. In this case, in the space between the sheathed pipe 1 and fluid pipe 2, flexible pipes or bars, for example silencing tubes, having a dynamic friction coefficient of 0.4 or less are positioned keeping their shape unchanged. The silencing tubes 5 are made to abut on the inner surface of the sheathed pipe 1 and the outer surface of the fluid pipe 2. This constitution makes it possible to easily insert the silencing tubes 5 in the space between the sheathed pipe 1 and fluid pipe 2, also eliminating the clearance of the fluid pipe 2 and surely preventing the fluid pipe 2 from generating vibration and noise.