At short ranges the phenomena relevant to the propagation of motor vehicle noise include inverse square law, interference between direct and ground reflected waves, the finite impedance of the ground, refraction, and turbulence. The interference between direct and reflected waves is a rapidly varying function of receiver distance and height from the source. If the ground has a detectable finite acoustic impedance a shadow region is produced which is penetrated at low frequencies by a ground wave. For ground having impedance discontinuities a diffracted wave originates at the interface. Strong wind and temperature gradients close to the ground produce a refractive shadow that is penetrated by a creeping wave. Wind and temperature fluctuations (turbulence) cause sound energy to be redirected by scattering and enhance sound pressure levels in the vicinity of acoustic shadow regions. In addition to the sound propagation phenomena, mechanisms associated with the moving vehicle cause variability in motor vehicle noise measurements. Experiments designed to separate the causes of this variability are discussed. The source of variability for moving vehicles can be either refraction in the turbulent wake of a moving vehicle or possibly the complicated diffraction pattern around a vehicle that changes rapidly with frequency.