Fig. 2
a Example of a recorded mosquito flight with ADC sample number (0 to 1023) on the x-axis and amplitude on the y-axis, scaled to a range of [− 1, 1], which equates to the full-scale range of the ADC. A high pass filter in the optical receiver attenuates frequencies < 300 Hz to remove electronic offsets and low-frequency noise, which also attenuates the signal due to the body of the insect. Baseline correction has been applied by subtracting the average value of the recording from each data point in the recording. b Power spectral density (PSD) plot of a typical mosquito flight. The wingbeat fundamental peak is labelled as f1. The fundamental frequency is indicated by the vertical arrow and the fundamental peak power by the horizontal arrow. The various peaks to the right of f1 are harmonics of f1, i.e. at frequencies of 2*f1, 3*f1, etc. The power density has units of (units2/Hz) on a logarithmic (dB) scale. A level of 0 dB/Hz corresponds to a white noise signal time domain signal with a power density of 1.0 unit2/Hz. The fundamental peak power density levels in this study are typically < − 40 dB/Hz, i.e. < 1 × 10–4 units2/Hz. The noise floor of the system, i.e. with sensor active but with no insect in the sensing zone, is < − 85 dB/Hz from 0 to 300 Hz and < − 90 dB/Hz from 300 Hz