The invention concerns expandable hose that reduces the hammering produced in hydraulic systems by pumps, with a tubular outer section of flexible material that has a fitting at each end and that loosely accommodates a tubular inner section of flexible material, leaving a hollow space between them, whereby one end of the inner section communicates with one of the fittings, allowing fluid to flow through it, whereas the other end is free and open, and whereby a fluid-conveying channel is left between the free end of the inner section and the other fitting. The use of expandable-hose sections of this type to decrease the noise of hammering in the power-steering systems of motor vehicles for example is known. The outer section is made from a material that isthe fitting at the steering end of the outer section, leaving a fluid-conveying channel at that point. The free and open end of the inner section is surrounded by an open cap that decreases friction against the core deriving from motions on the part of the inner section inside the outer section. Since the inner section is, like the outer section, flexible, it can be employed in cramped situations in the vehicle. Since a tubular channel with the same dimensions and purpose as the channels at the ends surrounds the inner section, pressure waves will travel twice through the tubular channel and arrive phase-shifted in relation to other waves in the fluid-conveying channel, accomplishing both reduction and mutual cancellation. The tubular channel left around the total length of