Variability in the passive ranging of acoustic sources in air using a wavefront curvature technique

Simultaneous time delay measurements from two adjacent pairs of sensors are used to estimate the "instantaneous" range and bearing of both stationary and moving broadband sources of continuous sound in air. The random fluctuations in the estimated source position are due to random errors in the time delay measurements. The variances of both the short time-scale and long time-scale random errors in the time delay estimates are quantified for different sensor separation distances and for different source positions. After normalization, the observed variances of the short time-scale random errors in the bearing and range estimates are found to agree with the theoretical results predicted for various sensor-source configurations where the independent variable is the length of the effective intersensor baseline. Increasing the intersensor separation distance by an order of magnitude reduces the bearing error variance by two orders of magnitude and the range error variance by four orders of magnitude.