Noise reduction is something that the boys and girls of the digital age hardly give a moment’s thought, but deep below London’s street, the very much analogue Tube network could do with Dr Dolby’s patented system. The squealing of steel wheels is hardly as melodic as Girls Aloud in full voice, and the characteristic caterwaul is a pain in the ear of which every London would gladly hear the back. The authorities are listening and doing plenty about it, but some think Transport for London (TfL) could do more to silence their critics.