The critical ingredient for pulling off a snob voice is pride. Voice actors cannot bring out the glory in snob voices if they're not proud. To be able to ignore someone completely takes a whole lot of confidence and self-importance. Snob voices should also flaunt the personal features and achievements they perceive to be impressive.
A snob is someone so full of themselves that you cannot convince them otherwise. You might have a hard time working with a snobbish voice actor, but the one thing you can be sure of is that they'll pull off the voice your project needs.
We have all interact with snobs throughout our lives. You could be a snob yourself, knowingly or unknowingly. Snobs take pride in being better positioned than other people. Thus, snob voices should give your audience the perception that your character is acting like they are because they feel superior.
The best audience to target with snob's voice is snob themselves, and people who have interacted with snobs. Casting a snob's voice is supposed to elicit an intense reaction from your audience. Many people have a dislike for snobs because they're always out to make people feel inferior and second-rate to them.
Snob voices are characterized by an air of importance, pride and superiority. It is funny how snobs cut people off, yet they expect others to listen to them as they rant on end. Snob voices should also have qualities of poshness and condescension that comes from the feeling of being superior.