The invention relates to a piston engine comprising a rotatably mounted cylindrical drum (2) provided with a plurality of cylindrical boreholes distributed over the circumference thereof and containing displaceable pistons. Said cylindrical boreholes (3,4) comprise cylindrical openings (35.1, 35.2, . . . 35.9) on one side, which are temporarily connected to one of two control nodules (9, 10) according to the angle of rotation of the cylindrical drum (2), said control nodes being respectively connected to a working line (27, 28). A reversing region (30, 31) is respectively embodied between the control nodules (9, 10), a first end (32) of a pressure compensation line (33) ending in one of the reversing regions (30, 31). A second end (34) of said pressure compensation line (33) ends in the output-side working line (27), the length (L) of the output-side working line (27) between the output-side control nodules (9) and the second end (34) of the pressure compensation line (33) being measured in such a way that a defined phrase relation counteracting the pressure variation exits between a pressure wave caused by a reciprocating motion of the piston (5, 6) and continuing in the output-side working line (27), and the angle of rotation of the cylindrical drum (2).