It was loud wasn't it? And the Avon/Spey crackle; "when shall we we three (in the case of the Trident) meet again?"
Always liked the... well, bubbly whistling noise the PW 707s made. Can't describe it better than that and also can't now recall how the Conways sounded on a 707 - and it's been a while since I saw (heard) a VC-10.
Still not as good as a Merlin though...