External axial rotary piston blower with noise suppressing transfer ports

An external axial rotary piston blower for quarter-roller type of construction with transfer ports leading to the outlet in the casing runway surfacing or inner peripheral surface of the housing with length differing relative to each other and increasing cross section differing toward the outlet, the greatest length of which can be permitted to be dimensioned or measured only such that the transfer ports are first opened when the inlet is closed-off by the piston traversing the same.