Measurements are presented of the noise produced by a 1.5 in. diameter air jet, with an exit Mach number of 0.66, impinging perpendicularly on a plane, rigid plate. The over‐all sound power output increased rapidly, as the nozzle‐to‐plate separation distance was decreased. The over‐all sound power generated, when the plate was 2 diam from the nozzle, was 10 db greater than that produced with the plate removed. For a 2‐diam plate separation the over‐all sound‐pressure levels (SPL's) (measured at a radius of 24 nozzle diameters from the center of the jet exit in the horizontal plane through the jet centerline) were 15 to 18 db greater than those produced at corresponding positions with the plate removed, while for a 20‐diam separation, the increase varied between 2 and 7 db. The spectrum of the noise changed as follows as the separation distance was increased: (a) the peak frequency decreased, (b) the pronounced peak changed to a broad one, and (c) the magnitude of the peak decreased.