Of Teachers, Baldness, and Aurals

Have you noticed (I'm sure it's constantly in your thoughts) that some puns work only aurally, not visually? My niece asked at Thanksgiving:

• What's the difference between a train and a teacher?
  A train says "Choo choo", while a teacher says, "Spit out that gum right now!"

You have to hear it to get it, even if you're hearing it silently in your brain. On the other hand, this one works either way:

• What did the bald man say when given a solid-gold comb?
  "Thanks, I'll never part with that."

While we're on the subject: Ask someone out loud to define "aurally." Will they define "orally" instead? And does the former pun work only aurally or orally? If there's an aura about the issue, is it an aural issue?--Definitely not, but what is it? Aureate indicates something of a glowing golden color, not necessarily having an aura; auric indicates something simply golden; aureus is a gold coin; aurevoir is...um...french; auricular, interestingly, is both the same as aural and something relating to an atrium of a heart. Is there a word for "having or relating to an aura"? And should we avoid all uses of adjectives beginning with aur so that we don't need to inject a dictionary directly into our brains?