The most irritating noise on the radio

Yesterday I had the misfortune to tine in to 5Live's Victoria Derbyshire whilst driving and was increasingly wound up by that noise she makes when someone has made a point that she either can't understand or wasn't listening to. It's hard to describe but I would say that it's a quiet but irritating "nnnh". Listen to her show and you'll know it when you hear it; it really is incredibly irritating, rather like her whole show in fact.