charcoal filter responsible for weird sound?

weird sound from the exhaust area, most noticeable when car is cold but can also be present once its warmed up. Just as you touch the throttle (revs <2k) get a kind of ‘bongo drums’ hollow resonance sound from (what i presume are) the pipes

b&c claim its the charcoal filter and is nothing to worry about…

i have the stage 2 performance exhaust + pipercross

should i be satisfied by their explanation? what exactly does the charcoal filter do, and why is it making that noise?

Sound like TADTS