When a passive acoustic system is used to localize a stationary sound source in air, the bearing and range estimates are observed to vary, although the source--receiver configuration is fixed. The variability in the estimates of the localization parameters is ascribed to temporal and spatial fluctuations in the sound propagation medium. This experiment employs a wavefront curvature technique to measure the bearing and range of a broadband acoustic source. The technique relies on three equally spaced microphones whose outputs are cross correlated to produce estimates of the differential time-of-arrival of an acoustic wavefront at each pair of adjacent sensors. Three intersensor separation distances are used: 25, 50, and 100 m. The temporal variations in the bearing and range estimates are presented together with an estimate of the measurement precision. Finally, the magnitudes of the systematic errors in bearing and range (introduced by a nonstationary atmosphere) are discussed.