A theory of jet noise is developed from the observation that in low‐speed turbulence Lighthill's quadrupoles combine to behave like simple sources ∼∂2p(0)/∂t2, wherep(0)is the “incompressible” local pressure in the turbulence. An integral for the far‐field intensity involves the space‐time pressure covarianceRwithin the turbulent. Choice ofRin a worked example shows how pronounced directionality results from pattern “convection” (modified by fluctuation) in conjunction with the time retardation. Further directionality is accounted for in terms of a Green's function (discussed qualitatively but not worked out) for a point source at rest in the mean shear flow, describing the lateral refraction and diffraction.