Verrrry interesting! I never really thought about doing resonant absorbers like this, but biomimetics is a really smart path to go down for sound absorption. Big kudos to the researchers, this could be what finally cracks the case of practical, thin acoustic absorbers for the home... the big question (as ever in acoustic absorber discussions) for me is what the minimum effective frequency is. If they got it down to 100hz or so, this would be pretty earth-shattering.