My quietest is my Miele S7 and my loudest is my Kirby Diamond, neither of which are normally discussed in the vintage forum. Despite the noise factor of my Kirby, I couldn't love it any more.
In contrast to what I would have assumed, I have found that a lot of vacs have become much louder over time instead of quieter. I've had Hoovers in recent years that were real screamers including the original Hoover Windtunnel that I used to have. I remember that the motor did not wind up or wind down. It just abruptly went ON at a loud and piercing pitch. This is in contrast to my favorite vacuum sound of the early Hoover Convertibles that gently wound up to that low pitched roar.
