a paper machine has a headbox provided with a slice through which a pulp suspension discharges from the headbox , this slice being defined in part by an upper lip frame . the pulp suspension flows to the slice from a distribution header and a turbulence passage assembly which receives the pulp stock from the distribution header and continues the flow thereof toward the slice . an air tank is provided for containing air under pressure to act on the flowing pulp stock so as to damp pressure fluctuations in the pulp suspension flow , and this air tank is connected in part to the upper lip frame of the slice so that the pressure in the air tank will act on the pulp suspension in the immediate vicinity of the slice .