The sound generated aerodynamically by a relatively smooth disk rotating in its own plane was measured in an anechoic room. The sound field was broad band owing to random, acoustic, dipole sources caused by the turbulent‐boundary‐layer flow on the disk. The low‐frequency part of the spectrum was due to a uniform distribution of pressure dipoles over the disk surface. The separated flow from the disk periphery had a well‐defined periodic vortex development and was the cause of the low‐frequency sound. The high‐frequency part of the spectrum was due to a distribution of pressure dipoles very near the disk periphery confirming Powell's [J. Acoust. Soc. Amer.32, 982–990 (1960)] prediction of edge noise. When the surface roughness was one‐tenth the boundary‐layer thickness, it was found that significant high‐frequency sound was generated at the point of roughness, indicating that apparent shear‐stress dipoles can be important sound sources. The sound‐power level was found to be 70.5 Db for the relatively smooth disk.