Good reply but lets delve deeper into:
"It all depends on the definition of ?sound,? and to a lesser extent, ?hear.?"
A sound, the vibrations of the air molecules, exists whether any human is there to intercept them.
At its core your ear, your nervous system, your brain, and your consciousness are merely chemical systems. A collection of interacting molecules and nothing more. Add a few molecules of aflatoxin and you can quickly follow the inevitable chemical reactions to the demise of system.
Human hearing is only of specific significance if one is so full of oneself as to think we are special. And that is something unacceptable in the context of science.
Your wife's dictionary is a layperson's dictionary and this is a science forum. Consider instead this definition:
"Very simply, sound is the vibration of any substance."
Source:
http://library.thinkquest.org/19537/Physics2.html I still think you owe her an apology. Remember: There is a price to be paid for being right on a technicality. <g> And a dozen roses costs less.
