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Description
Automated signaling of pest insects in the field could drastically improve the cost-effectiveness of integrated pest management. Acoustic monitoring of flying insects has the potential to be a low cost solution with spatio-temporal resolution for timely intervention. However, it is not used in practice due to high background noise levels, which obfuscate the insect sounds.We propose an improved trap design to enable acoustic monitoring of pest insects in practice. By tuning the acoustic filter response of the trap we aim to increase the signal-to-noise ratio to a sufficient level. We employ a multiple Helmholtz resonator configuration to attenuate noise coming from outside of the trap at the entrance. Sound recordings of flying Delia antiqua were analyzed to determine the distribution of fundamental frequencies. A side-branched Helmholtz resonator array trap was then designed to attenuate environmental noise at the wingbeat harmonics (~175 Hz multiples). The acoustic response of the full trap was tailored to the respective frequency bands with finite-element simulations, and validated experimentally. Also the position dependent response of the trap was characterized to ensure that the insect sounds produced within the trap were not deformed as much as to make recognition fail. Simulations predicted a signal-to-noise ratio improvement of 10-25 dB in the frequency bands of interest, while experiments demonstrated gains between 5-20 dB. The dependence of the microphone signal on the position of the insect in the trap was found to be sufficiently smooth to avoid that effects of the insect position would confuse recognition.