Now you hear me, now you don't - anti biosonar stealth of resting moths

Some moths gain protection against echolocating bats by stealth acoustic camouflage, absorbing rather than reflecting bat sound. Stealth camouflage is only adaptive in flight though. Frequently, moths are resting on substrates from which bats glean them. High absorption lets resting moths stand out as a non-reflective 'black spot', while matching substrate reflectivity would provide camouflage. We believe that the resonant wing absorber offers both functionalities - being highly absorptive in flight and highly reflective on a substrate, by exploiting the viscoelastic boundary layer that covers every solid surface. Moths would only need to adpress their wings to their resting substrate, and many species (e.g. Geometridae) do exactly that.
In this interdisciplinary project, we will confirm and quantify that moth wings have bimodal resonant functionality by these complementary approaches:
(a) echo-acoustic tomography to quantify the boundary layer effects (details in rotation project 2)
(b) thermoviscous modelling of the absorptive properties (details in rotation project 1)
(c) theoretical exploration of bio-inspired carpet cloaking metamaterials and publication of work on iso-spectral twinning.
As bat work wasn't possible during Covid lockdown, the project successfully shifted towards theoretical aspects. A detailed fundamental understanding of bio-inspired carpet cloaking has been achieved. Theoretical developments then led to a seminal publication on isospectral twinning of cavities, which develops the discoveries made on moths into an analytical model that then is applied to a range of scenarios. So the work has far exceeded the targeted empirical approach and resolved and translated the metamaterial physics behind the moth carpet cloak. This exciting innovative project indeed put the emerging field of acoustic camouflage to the test, and realised some of the exciting new insights, as well as opening future opportunities for the successful candidate.