The U.S. Grain Inspection Service, Packers, and Stockyard Admininstration’s (GISPSA) standard quality assessment method involves sieving and visually inspecting a one kilogram sample: their guidelines “consider grains infested if the representative sample contains two or more live weevils, or one live weevil and one or more other live insects injurious to stored grain, or two or more live insects injurious to stored grain.”
However, since the larvae of many stored product pests grow inside grain kernels, where, Fleurat-Lessard notes, their “population density may be ten times more numerous than free-living adults,” a visually-inspected“clean” sample may actually be completely infested with rice weevil larvae. To look inside grains, laboratories use X-rays or resonance spectroscopy, but these techniques are too expensive and impractical to deploy in bulk grain lots.
But while rice weevil larvae are invisible, they are not inaudible: the “mean sound pressure” of rice weevil larvae feeding inside a wheat kernel is 23 dB, according to the USDA Agricultural Research Service. The idea, then, is that if you could somehow design sensitive-enough acoustic probes, combined with software to match the probes’ input against a database of field recordings, you might be able to monitor insect activity in stored grain automatically and detect infestations at the larval stage.
I had no clue such a thing as acoustic pest detection existed. Amazing.
Building a sound library of stored food insects was equally important – the field recordings on that Insect Noise in Stored Foodstuffs CD actually form the core of current acoustic pest detection databases. Years of research have gone into classifying the characteristic sonic signatures of different pest species at different stages in their lifecycles, to the point that a computer can now compare input from a grain silo’s acoustic sensor system against a library field recordings and tell you whether the rice weevil larvae eating your wheat kernels are sixteen or eighteen days old.
The smartphone is a form of human augmentation, the latest version of the “bicycle for the brain” metaphor from Steve Jobs or whoever it originated with. I'm looking forward to more sensory augmentation in compact form factors in my lifetime. The ability to increase the sensitivity of my hearing and have it plug into a database of sounds for enhanced recognition would open up a whole new world. Camping would never be the same again.