The received Doppler signal of a stationary sensor, as emitted by a transiting acoustic source, is used to estimate source motion parameters, including speed, closest distance, rest frequency, and closest point of approach (CPA) time. First, the instantaneous frequency, amplitude, and CPA time are accurately estimated by the polynomial chirplet transform of the Doppler signal. Thereafter, the three other source motion parameters are obtained with a simplified amplitude-weighted nonlinear least squares method. The proposed scheme is successfully applied to the analysis of the characteristics of a moving truck.