Investigation of passive acoustic anemometer by use of wind noise correlation

This paper examines feasibility of an acoustic anemometer by evaluating the estimate of wind directions and wind velocities towards microphone array. These estimates are calculated based on a number of delay times among pair-microphones. A low-frequency correlation between wind noises for pair-microphones is practically utilized in order to obtain the delay times. First, the validity of the estimation method is evaluated by simulated wind noises, and then some high-precision results are obtained. Next, the estimate accuracy of wind directions and wind velocities for recorded wind noises are evaluated. Winds are generated from a tower fan and recorded by three microphones that are closely located at each vertex of the triangular. The result for the recorded wind noises shows that estimate errors are heavily dependent on recording direction in contrast to the results for simulated wind noises. Since these fluctuations of errors are commonly observed in several recorded wind noises, a correction for unknown estimates is approximately calculated by employing some known estimates and their errors. As the result, average relative error of wind velocity is 5.4% and average absolute error of wind direction is 6.64 deg. This correction method indicates the efficacy of estimating the wind directions and velocities.