Two-Axis Anemometer with Acoustic Reflector Using Single Pair of Loudspeaker and Microphone

Abstract

In this paper, we describe a two-axis anemometer with an acoustic reflector using a single pair of a loudspeaker (SP) and a microphone (MIC). The two-axis anemometer proposed in this study consists of a SP, a MIC and an acoustic reflector, which form a right-angled isosceles triangle. This anemometer can measure spatial mean wind velocity and direction by calculating each wind component along the coordinate axis defined in each propagation path; this anemometer is targeted for use in air-conditioning systems of high efficiency. The sound probe consists of a SP, a MIC, an acoustic reflector and each propagation path. By using the acoustic reflector, an additional sound path becomes available. In this case, the time of flight (TOF) can be measured using a single SP–MIC pair because of the difference in TOF between direct and reflected waves. Some experiments were carried out in a wind tunnel to measure wind velocity and direction at various wind velocities. The sound probe is placed on a turntable in a wind tunnel. Although the actual wind direction is constant, the apparent direction relative to the sound probe can be changed by rotating a turntable. The measured wind velocities and directions in the experiments showed only small changes with the wind direction change. The feasibility and accuracy of the proposed two-axis anemometer for wind velocity and direction measurements were confirmed.