It would be wrong to describe Cathy FitzGerald’s excellent documentary (5 June) as a meditation on the idea of silence. Rather, it was an inquiry into what the natural world might sound like once you removed humans from it. What followed was, at times, little short of cacophonous: frog choruses booming away; individual creatures straining to “find their bandwidth”, as one expert put it, a collective wolf howl from the forests of Alaska that sounded like a vast and infinitely sinister orchestra tuning up.