Ultrasonic characterization of insect wing reflectivity and wing-beat motion at 200 kHz

A bistatic active ultrasonic sensor is used to detect and identify an insect attracted to a pheromone lure in the beam intersection. The ultrasound beam is a continuous waveform (CW) of approximately 200 kHz to avoid detection by the insect auditory system, which is very sensitive near 40 kHz and below to detect predatory bats. Both amplitude modulation (AM) and frequency modulation (FM) of the CW beam are examined. The reflection factor of the wing material is measured using ultrasonic pulses. The near-field interference nulls of the transmitting beam are modeled and measured to ensure that the lure is not placed in one of these zones. While good AM and FM signals are seen in the received waveform, the pivoting and flapping motions of the wings along with the insect movements create a complex pulse-train like waveform. This is seen to be inherently due to the narrow beam-width for the transducers and a lack of nonspecular scattering from the moving wings. The data show that a simple AM detector can be used to detect the presence of an insect at the lure and to measure the wing-beat frequency. [Work supported by USDA].