The type You refer to would be good to know. If it is the DH8, the lower innards of the engine intake are made from composite material; the honeycomb structure of the middle layer is rather well visible. As the main source of noise is the propeller and not so much the compressor (which is pretty much shielded behind a rather complicated duct structure), there are none of those noise reducing resonance holes that can be found on jet engines.
So my money would be on a bare composite structure that just happens to look like this without any bad intentions behind it.