The measurement of acoustic pressures in moving air streams

The self-noise of several windscreens has been obtained at velocities from 5 to 15 m/s and frequencies from 90 tot 3000 c/s. The study indicates an optimal screen flow resistance of 0.06 ϱC. Streamlining a circular cylinder may reduce the noise 3 dB at frequencies 300 to 1000 c/s. The spectrum level of the noise varies as the 6th power of the air velocity near 250 c/s and as the 8th power near 1000 c/s.