My cat is a snob. He was terrified of every single vacuum cleaner we've had (IMO, they were all shit, including the fucking Dyson) until I gritted my teeth and ordered a Miele. Now, he merely makes a discreet exit over the top of the settee and through the banisters if it comes within three foot of him. Considering the OH clatters around like a herd of elephants with all vacuum cleaners, brooms (cat attacks them if he's in That Mood), I don't think there can be that much of a difference in the sound, other than a vague difference in pitch.
The other one was scared of doors. In my old flat, we had them (reasonably enough), but never closed more than the outside ones and the bathroom. If one were moved so that it was ajar, rather than pushed right back, she'd saunter in, spot it, jump out of her skin and then hide. And anything out of place. Drop a crisp packet on the floor or take your shoes off whilst she was out of the room and she'd be horrified on her return. But we can move furniture around in this house and she doesn't give a monkey's - it's open plan downstairs.
Both are terrified of 'proper' Geordies. Couple of our friends are from up there, both love cats - one, with a broad accent, sends them running for cover the moment they hear his voice, the other, whose accent is much, much softer (but makes just as much noise), they'll hurl themselves upon him for acknowledgement and fuss.
They both have absolutely no fear of small children (none in the house, but they will parade themselves at the front window during the school run so the little ones can admire them from afar bang on the window to say hello )
Horses are definitely the worst. As a prey species, I can understand it, but seriously, you've walked this same route every morning for the last six years, rain and shine, winter and summer, but now you decide there's a single fucking leaf out of place on the same fucking tree and it obviously means imminent death from a pack of wolves? Twat.